Like you might expect, I can't remember the title or the author, but I remember enough details that perhaps a helpful librarian or bibliophile might be able to help.
- I read it about 10 years ago, and I believe it was new at the time.
- It is science fiction.
- The protagonist is a fabulously wealthy man with a kevlar-reinforced skull.
- He and his girlfriend are immortal, but this immortality is surgical in nature; every 20 years or so, they need to have their genes re-set in a hideously expensive and complicated procedure. In fact, it's so expensive that it bankrupts whoever has it done.
- Somewhere along the line, they discover that the procedure is being deliberately botched; done properly, the recipient never needs to have it done again.
- They flee to the asteroid belt and take refuge in a colony called Novosibirsk.
- They are pursued by bad guys (naturally) who like to incapacitate their victims with a drug called zombie, which slows the victim's perception of time such that seconds seems to last minutes.