I received a medium-sized non-dormant plant last summer from Ron. It ended up dying back to the roots. At the time, it actually appeared to have rotted back to the roots. I ended up forgetting about it, but in the fall, to my suprise, it came back looking as good as before!
I'd say that if you're going to repot them, definitely do it when the temps are cooler. My D. trinervia from Crystal have yet to go dormant even in temps above 90F, but this guy didn't survive trasplanting in 80-85 F temps.
I've found the same to be true even with repotting Drosera capensis in higher temps though.
But it seems that whether or not D. trinervia dies back after transplanting, you can be fairly assured that it will come back for you.
As a side note, I didn't allow the media to dry out at all. Can't be sure, but it may have helped that it only had an inch long root? I have no experience with true dormancy with D. trinervia so I can't really make a comment for sure about moisture content during dormancy...
If you're looking for germination tips, Crystal grew the plants she sent me from seed. Sounded as though she started them the same as she does her D. capensis.