Making your trip longer is almost always a good thing to do, if you can get away with it: longer trips let you get more from the cost of your flights. If you blow a bunch of money to fly to Europe and back (and flying to Europe is never really "cheap", especially lately), but you only stay for the weekend...woo, your cost per day for your air fare is painful; stay 3 weeks and the cost per day drops way down (of course, the longer you stay, the more your total trip cost will be, so everyone needs to strike the right balance for them).
It always better to slow down a bit and savor the experience, rather than rushing....if you can manage. Most people are primarily constrained by the number of days they have, si it's very tempting to try and cram in too much (a common pitfall for first-time travelers). With more days you can slow down a bit, and/or go to more places (again, the key is striking the right balance for you).
One suggestion for future posts: You'll get better results if you give your post a title that better describes what you're asking about. (For many people these days, "AirBnB" is an app on their phone.) 😎