To Answer your question stef (note, i understand this thread is OLD but i need something to do!)
the internal flash is good for 400 000 000 write cycles. thats some 2000 flashings.with normal use. Same goes for the SD cards (at least normal ones, "Ultra SD" cards can handle about 800 000 000 000) and the CF Cards (same applies for "ultra" cards)
BTW, Hybrid rom came and went... is there a way to stealthily overlay 1.6 or 1.7 on top of 1.5?