Even on long flights I don't mind switching in F. I dont like bulkhead but am 5'3 so it seemed petty when a 6'4 guy asked to sit by his teen son to say no. There was no overhead room for my bag though so I made him put it underneath his seat and give it to me after we took off! He was happy to do it but it was a little odd of an arrangement.
I asked on a short 1 hour flight recently with family to sit next to my stepdad (we were on different tickets and I got upgraded last as Silver so had no seat choice). It wouldnt have been a big deal if they said no, and I normally wouldn't care, but we rarely get the chance to chat 1 on 1 in a big blended family. Traded a window for window though. Rest of the family was in coach
. We cheersed them with our free drinks when they boarded in zone 4!