Cartridge questions

I am pretty sure that my questions have been asked before, maybe worded slightly differently, but nothing too useful came up with Search, so here we go.

1) For how long do those of you with a DV cartridge, say the XX2 MKII, expect to use it (observing the mile long list of caveats, I am just looking for a rough range)?

2) No question that replacing a cartridge is best carried out by an expert but, none of those being all that near to me, how risky would you consider a DIY job to be?

Thanks in advance, Per.