NEW YORK (MONEY Magazine) - Q. What happens if my situation changes?

If your former employer drops your retiree drug benefit, if you move out of your drug plan's service area or if you lose your drug coverage for any other reason that's not your fault, you'll be able to sign up for a new Medicare drug plan during a special enrollment period.

But if you've delayed enrolling in Medicare Part D because you just couldn't make up your mind about what to do or you simply want to switch to a different drug plan, you generally can do so only once a year, between Nov. 15 and Dec. 31.

Your own situation isn't the only factor that may change. The new drug benefit will likely change as well. Premiums could rise based on the number of drug claims filed. Deductibles, out-of-pocket maximums and co-payments could increase as drug costs generally rise. And the list of drugs that each plan covers will undoubtedly change too.

"There's no way to know exactly what will happen in the future when you sign up," says Hayes of the Medicare Rights Center.

Just because you don't know what changes may lie ahead, though, doesn't mean you should hold off signing up for drug coverage now. Chances are your medication needs will rise as you age, and even an imperfect benefit is better than no benefit at all, most experts agree.

"It's sort of like homeowners insurance," says Neuman of the Kaiser Foundation. "You buy it before your house burns down, not after the catastrophe."

What about your other coverage? >>

_____________________

Click here for more on MONEY Magazine's special report, The Dream Retirement.