I had both resurfaced, the left first in Aug/2009, and the right Nov/2009. My surgeon, Dr Su at HSS, suggested 3 mo between them, which is what I did, pretty much to the day.
The SECOND (right) hip, which was worn down completely but not in such bad shape as the first, has recovered quickly--much more so than the left one, which still doesn't have as much range of motion or strength as the right, although it's (the left, first side) is doing well.
I wanted to get them both out of the way as soon as possible, and I didn't want the second to go past the point of no return (although I don't know exactly how that is defined). I also wanted both in the same year for insurance-related reasons. I've heard (from the surgeon) that the second often goes better than the first--perhaps bc you know the ropes, and bc it wasn't as bad off to begin with as the first one.
I have no regrets about the timing of my surgeries, and I'm glad I didn't do them both at the same time. Don't think I could've dealt with that very well--sleeping issues, etc.