Does it make sense to fly in and out of Lisbon?

I will note that we found that cruise (?) departures can book Lisbon air seats up often. But going home (or to) via Madrid is time-consuming and annoying. We found the Lisbon airport entirely satisfactory, even for a roundtrip to see Madeira. As for Porto, I have found two-segment flights to Europe to be satisfactory. But some posters here who had a bad connection (not talking about "Porto") swear they will never do it again!

We've found that taking a second segment on the right airline can cost less than ground transportation. 4 weeks is a long trip just between Lisbon and Porto, it seems to me. We drove that route as well. GPS was essential. We even spent a night at the (greatly diminished, not recommended) Hotel Busacco Palace.

We flew in and out of Lisbon. We picked up a car outside of Lisbon and drove over a couple weeks toward Porto. We returned the car in Braga, took the train to Porto and then the train back to Lisbon.

If it works for your itinerary and budget, I see no reason to not fly home from Porto. I don't think I would fly between Lisbon and Porto. By the time you get to and from the airports, it doesn't seem time efficient to me.

Thanks so much for your replies. We found non-stop flights in and out of Lisbon with TAP Air Portugal, so that's what we're planning.
And, taking the Alfa Pendular Train from Porto back to Lisbon. Happy travels!

One thing to think about is to catch a train on arrival day to Porto. That way you can consolidate all of your Lisbon days at the end.
I always figured arrival day was a lost day anyways, so might as well catch a train and nap. Also, if you haven't already, take a look at the Minho region north of Porto. We spent a few days there and it's a wonderful area that gets overlooked.

Thanks for mentioning the Minho region, it looks very interesting! We'll check it out. We're planning an itinerary for about 4 weeks, and we like trains. So, we're thinking about splitting about 8 days in Lisbon spending them at the beginning and end also gives us a nice train ride. We're also planning on private transportation to travel from Lisbon to Porto, with stays in Evora and Coimbra with day trips.

South to north or vice versa doesn’t matter. You could do a loop and start and end in the same city. We had a rental car and made a loop of our Portugal stops. Which you do will depend on how you’re getting around and where you plan on stopping.

We flew in and out of Madrid since a rental car was much less expensive than renting in Portugal.

I went ahead and added a link to the Julie Dawn Fox blog which I used for the Minho region.

https://juliedawnfox.com/tag/minho/

Braga and Guimarães are popular as daytrips from Porto, or you can stay there. We used Ponte de Lima as our base which is on the Camino de Santiago pilgrimage route. We were originally going to drive across the border into Spain to Santiago de Compostela but this was during covid when borders were not always open. But I thought I'd add this for ideas since you have 4 weeks.

Thanks Gail! I used your link for Julie Dawn Fox: https://juliedawnfox.com/tag/minho/. I also used her ideas for hotels.

Fly into Lisbon and out of Porto.

It does make sense to fly into and out of Lisbon. I hopped on a fast train to Porto when I arrived, spent a few days there, and then finished up in Lisbon (again, fast train from Porto to Lisbon). Easy and inexpensive.

It makes sense for me since flying in and out of Lisbon is much less expensive and I’d have to do a layover in Lisbon to get to Porto anyway. I’m also catching a train straight to Porto when I land and will end up back in Lisbon several days before flying out.