Do you do it? And if so: when?
I have an unwritten rule that I'll have a piece over £250 altered if it doesn't fit perfectly. My co-worker, however, tells me it's madness to be spending money on alterations and that no one will notice minor fitting issues.
If it makes a difference: I have a small waist/big bum. Just hate the pool of loose fabric that tends to accumulate across my lower back if I don't have certain otherwise well fitting dresses taken in a bit.