"Power yes, immortality, no," He replied. "And there is only so much genetic augmentation a body can take before it breaks down."
Which was why Rogue's DNA was so important. Her body, her DNA, did not suffer, did not decompose after using and manifesting other mutations. Her body was made to have infinite possibilities at her fingertips. A body made from her DNA would last much longer, take more changes and genetic enhancements than any other.
"I will need to do so again in roughly thirty years, assuming my current form isn't destroyed and I have to transfer myself to a new body."