I went from:
285/60-18 Inflated Dia.= 31.50 Width= 11.50
to:
275/65-18 Inflated Dia.= 32.3 Width= 10.5?

I flipped the bj's, cranked the t-bars, and added 912's after having the 285's for awhile. After a few months, I mounted the 275's. I have heard people say over and over that 1" doesn't make a difference - well I totally disagree!!! With the same wheels, but different tires, I lost about 1" in width, but gained 1" in height. Now my antenna hits the garage door opening; it didn't before. My VX also looks much different - I think that 275 height fills out the wheel wells perfectly with the 912's lift, yet I thought the 285's looked a little squatty and small for the mild lift. Going to 33's (yep, one more inch) I would have to do more trimming or add more lift - probably at least an inch...

So I would say if you want to go bigger, just go bigger. If you want to go bigger than that, expect more work and wear and tear. Since you are running 18's, consider how helpful the extra sidewall of the bigger tires would be offroad. Good luck and I hope to see you in Moab!