I didn't time mine, for me it was closer to 45 minutes for the focus to finally stabilize.
For me when cold the best I could do was an 85 inch focused picture, after (about) 45 minutes it would do 110+. It took me a few days to figure this out (once on, tinkered with then sat and watched) it wasn't till the 3rd day when I felt everything was set (no more tinkering required) so I started up the projector (figuring it would be where I left it) and it was horrible (I'm thinking what went wrong). Then as time passed and it warmed up the picture got better, then I understood.
It is a rather small enclosure for the # of watts used so I figured maybe a stiffener was forgotten, screws loose, etc. I never thought of it as a design issue more of a first production run issue. Where some have limited to no shift I figured it was just my projector.
I sent mine back and didn't get a replacement, I figure with this first production run these problem will take a few months to weed out, I'll wait a few months for Vititek to resolve this issue. I sent mine back (mine was an extreme) and I know others have sent theirs back (guy at the very beginning) and I'm sure engineering will identify and resolve this problem.
Back to waiting