Well. From a lazy person's point of view- they only say that so they can't be held accountable in case you lose depth.
I had my surgery with Chet in early December 2014, so like 6 months ago, and I dilate like 2 times a week approximately, for an hour, I was decreasing the frequency as time went by, seeing how long I could wait before I noticed a difference in discomfort during dilation.
It's too big of a chore to pull off 2 hours everyday for 2 years, gurl bye, there's more fun things to do
edit: oh, and i haven't lost any depth. fresh after the packing removal i was told 6inches, but I assume they overestimated as it often happens, the swelling went down rather quickly and I've been at 5,5inches ever since.