Hairline and crown FUE in one session? (3,500)

I've met with a few hair transplant doctors, and they've all advised roughly 2,000 units in the front and about 1,500 in the crown. The only discrepancy I'm getting between the doctors is whether it can be done in one session. Not because of the larger quantity of grafts, but due to "optimal healing". Some say results won't be optimal if the front and back are both trying to heal at the same time/blood flow etc.. best to do front and back separately. Thoughts?