Can I sit for a long period of time at 5 weeks post-op of a brazilian butt lift?

At five weeks after the surgery you should be fine to sit in the car for that long. I would recommend that you get up every hour or so and walk around in order to change positions. You might also consider sitting on a pillow. 

Hello dear!!
Thanks for the question and provided information as well.
Each doctor has their own protocol. It is very important that you talk to him about your concerns and goals. I recommend my patients not to sit for more than 30 mins. every two hours, for the first 2 weeks, and always with the help of a boppy pillow. If you have any concerns, I suggest you follow up close with your plastic surgeon.
Hope this is helpful. Good luck :)

Thanks for the question. You should be able to go on vacation by 3-4 weeks after your surgery. But this is valid only with assuming postoperative recovery is uneventful. If any unexpected incident happens in your treatment process, this time can be extended or shortened. I wish you all the best.