Honolulu, Hawaii; Length of Stay?

Can you prepare food where you are staying? That can help the budget a lot. I wouldn't go all that way for five days ( that is just me) as the jetlag might cause you some difficulty only to get somewhat on Hawaii time then having to flying east to get home. Jetlag is worse when flying eastward. See if you can work out the eight days by cutting out a few things that you might want to see. You can't see it all so plan to go back someday!
Have a nice trip.

I think you and your boyfriend will need to work this one out yourselves, but there is no reason why you couldn't have a great vacation in either time frame. There is no required minimum or maximum to have a good time anywhere. You simply have to prioritize what is important to you. I personally don't like Honolulu very much. 1-2 days in the city and I am done. I love visiting areas around the island and checking out beaches that are not as busy.

Maybe you and your boyfriend should consider checking out a few guidebooks and also discussing what is the goal of your vacation. It can be a little surprising to discover your travel companion has an entirely different idea of what the perfect vacation is. You may have different travel styles and talking about what you what to do in advance can help keep those surprises from showing up in a stressful manner while on vacation.

Have a wonderful time.

If u can, get out of the city and head to the north shore. Big waves and more of a laid-back vibe. 7 days is good, 10 is better. You could spend much more time and not see it all. Just go!

without breaking our budget?

Hard to offer meaningful comments when the 'budget' is a mystery..

Flight times are 5.5 -6 hrs, not 8 hrs.

If you have free lodging, presumably with a kitchen, your food cost differential is minimal. If cost of food for 2 days is a budget buster, you probably shouldn't be going.

If you take an AM flight to HNL and an evening flight back, you have at least half a day there on your travel days.

Renting a car? Last time I rented in Hawai'i, a one-week rental was actually cheaper than shorter-term (don't ask why.) Check it out, and maybe you can show him that the longer trip is really more economical.

If you'll be staying in Honolulu, you'll still want to get out of the city and explore other places in Oahu, like Kailua, the Polynesian Culture Center (forget what exactly it's called), the north shore, and some of the temple ruins. So you'll want to rent a car for at least some of your days there. Too bad you won't be visiting another island as well.

Just on Oahu I think I'd find five days was enough, not being a surfer or big beachgoer. But you may prefer longer even though it will cost a little more (just meals and transportation I guess). Use a guidebook or two to figure out what you want to see and do, and how much time that totals, remembering that it's a vacation not a forced march. Build in some down time.

Joe is right about flight time from the west coast, but I'm guessing you'll be flying from the east or midwest, so of course takes longer.

The longer the better....but I'd go if only five days on Oahu were possible. As told to me years ago by a fellow tourist in Hawaii during a rainstorm, " A bad day in paradise is better than a good day in ______________ [your city]."

Having lived on Oahu for 5 years I really think you will be able to do everything you would like to do / see in 5 days. If you were including another island I would say 8 days would be great, but since it sounds like you are staying for free then 5 days should be plenty.

...everything you would like to do / see in 5 days.

I would suggest getting a good guidebook (Hidden Oahu?) and make a list of your must see/do and would like to see/do places and activities. Decide whether you want to be on the go 12 hours a day or 4 hours a day and plan accordingly.

A Hawaiian holiday is not like a check off the list European museums and church stain glass windows holiday. A Hawaiian holiday is or at least should include rest and relaxation time including watching the sunset (or sunrise) and enjoying a fancy drink with pineapple spear and vanda orchid. Some visitors even like to lay on the beach (sunscreen?) with time to dip into the tropical ocean water. Others may enjoy a leisurely mountain hike to a hidden waterfall.

Assuming that you are an employed working couple, a compromise could be eight days. Depart Saturday morning (arriving HNL mid day - time difference) return the following Sunday on an afternoon flight arriving late night. That gives you six full days and a half day on each side. Depending where you are staying in Honolulu, have a nice early lunch on the way to the airport. If you are on the Diamond Head (Waikiki) side of the airport: Nico's Pier 38 is good, cheap and fast).

Following on from Edgar’s suggestion, Nico’s is a great eatery but is nowhere near Waikiki; worth the taxi ride though.

Things to do in Honolulu: if interested in the history of Hawaii before Statehood visit the Bishop Museum, absolutely fascinating; Pearl Harbour and the Arizona Memorial are a must see as is the National Cemetry at Punchbowl. Take a hike up Diamond Head; wander through the Royal Hawaiian Hotel and maybe have a drink there or under the Bayan tree at the Ala Moana hotel. Take a ride on a catamaran and snorkel with the sea turtles off Waikiki beach, wander through the rather gritty Chinatown. Discover the many ways Hawaiians cook Spam, or try a loco moco, poke or other Hawaiian dishes in a Hawaiian food tour. Take a tour, a bus, or rent a car and go to the North Shore for breakers, beaches and shrimp trucks. Eat shave ice. Above all, if the place you are staying at has a pool, just hang out and relax. Aloha!

I'm in the 5-day camp. I spent that amount of time there last year and thought it was a fulfilling trip, covering a lot of things without being rushed. Our hotel actually had some really nice restaurants. A good eclectic mix and able to accommodate different budgets. Just FWIW. Also, we spent an afternoon at the U of H flea market. Fun, local-feeling, budget-friendly way to spend a few hours while being outside.

Also, we spent an afternoon at the U of H flea market.

If you are in to "flea markets", the Aloha Stadium swap meet is BIG: http://www.alohastadiumswapmeet.net/content/about_us.aspx

SWAP MEET: Sun 6:30am-3pm Wed,Sat 8am-3pm MARKETPLACE HOURS :
Wed,Sat,Sun 8am-3pm
The Aloha Stadium Swapmeet & Marketplace is open three days a week,
offering endless rows with hundreds of local merchants and artisans
with the best value on imported merchandise, hand made items, eclectic
art pieces, popular local snacks, and other made in Hawaii products.
This is sure to be your one stop destination to find that special gift
or souvenir for everyone on your list.

If you are in to "flea markets", the Aloha Stadium swap meet is BIG: http://www.alohastadiumswapmeet.net/content/about_us.aspx

Yup, that's what I was thinking of. Pardon the east coast parlance :) Was a nice way to spend an afternoon. Picked up a few nice souvenirs.