I wouldn't change your email address unless it's absolutely necessary. Your stats will then split into active projects and dead projects. When you change your email address for a project then you also are changing your CPID.
I changed my email address years back and now there are 2 biodocs at Free-DC. The "new" one and the "old" one. I never figured out how to fix that problem. If someone has a solution to this issue, then I'd be keen on hearing it.
If you don't care about losing the stats/points on retired projects, then it's not an issue.