I suspect that telomeres are just one component in a system that maintains an organism's biological stability, and that simply lengthening them without reference to the rest of the system will just get you a young, cancer-ridden body.
Yes, sometimes the problem is that a cell refuses to die. SENS has come up with a list of 7 general problems (it's increasingly unlikely to be any more) that collectively form the problem of "aging" and need to collectively be addressed to cure aging. Death-resistant cells is just one of the 7. http://sens.org/research/introduction-to-sens-research
