In General, I Agree
Generally speaking, I agree that the cabin you're in is where you go when you gotta go.
Exceptions for me are:
You're in Y, the back lavs are full and you're going to have a mid-air collision with your undergarments.
You're in F on a 752, the front lav is occupied and the mid lavs are not.
What really frosts me is when the pilots ring four bells at 10K feet, then wait another 20-30 min of smooth flying to turn off the fasten seat belt light and twenty people jump up to run for the loo. That's when the long lines seem to be the worst.