I practice and record seated, I rehearse and gig standing up. Changing back and forth is no biggie as long as you do plenty of both. If I haven't played standing in a while there might be a slight adjustment period, but it's only one song or a few minutes. I usually rehearse at least once a week minimum, so I'm good to go either way.
Same here. I practice daily and rehearse weekly. In my project studio I sit. At rehearsal and gigs I stand.