A 100th birthday is so rare these days that it’s cause for serious celebration. But scientists say that someday in the very near future, people could live well beyond that.

“I don’t think there’s any limit,” said Aubrey de Grey, a leading longevity researcher and scientist at Cambridge University. “Certainly, there’s nothing that would stop people intrinsically from living thousands of years.”

How? Some researchers say it’ll involve finding a way to keep cells from aging, while others believe the secret to agelessness lies in growing spare parts — such as blood vessels, hearts and bones — to replace those that are too old to function properly.

Molecular geneticist Bill Andrews has discovered a supplement he thinks will reprogram cells, causing them to live forever. Since scientists believe that aging occurs when the strings of DNA that reside at the end of each chromosome — called telomeres — become shorter, the supplement stops that from happening or even causes telomeres to regrow.

“The literature is, I would say, 95 percent certain or better that if we can find ways to lengthen the telomeres, we are going to reverse aging,” Andrews says.

In other words, your retirement fund may have just met its match.