Are drains necessary after a BBL? How many days do drains need to be in for after BBL?

There is fluid that tends to build up in the body -  as we have just created space with the removed fat cells. So to improve the recovery period and to remove the excess fluid I keep drains in for 5-7 days. My inclination to remove the drains is once they reap less than 30CCs. This is a measure to raise the success rate and perfect your new look. My recommendation is that you find an ASPS board certified
surgeon in your area who specializes in the BBL, and set up an in person
consult. An in person consult with an an ASPS board certified surgeon is
the only way to determine the best route for your body and your goals.  

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.

Drains are not necessary after BBL, but you will find that each surgeon tends to use what he/she learned about the procedure or what they think works for them. I personally do not use drains, but I insist on daily massage of the areas above the buttocks, mainly the lower back, waist  and upper back to get the serous fluid out. I also use foam compression of these areas to further enhance the results. Although the back massage is tender right after surgery, this must be done. I often instruct my patients and their care givers on how to do this effectively. Conversely, a certified massage therapist can assist you if your care giver is squeamish. See a board certified plastic surgeon who understands and recognizes the beautiful normal to create your best possible BBL. Good luck.