Well, I'm 14 months out, and I did not cut my hair at all. I have a religious conviction against cutting my hair, so it's not even been trimmed since 1992. It went through a phase of looking thin and dry, but has really come back in the last couple of months.
And while I thought I looked half bald, someone at my church actually told me that she was impressed that I didn't seem to have lost any hair, unlike others who have the surgery. Go figure.
Some of the things I did to minimize loss/ encourage regrowth are: Using the best shampoo possible, getting in enough protein, taking Silica from Pilgrims Pride, and scalp massage.
I have a video about how to do a proper scalp massage on my blog. It's made a big difference for me. Heres a link:
Hair Loss After Gastric Bypass: Stimulate Regrowth With Scalp Massage
Hope that helps.