IT'S simply not enough for billionaires to have everything they've ever wanted – they need eternity to enjoy it, too.

At least a dozen of the world's richest men have ploughed millions into bizarre ways to live forever. Here are five of the weirdest.

1) Cure for ageing

A number of billionaires are putting their cash to good use by trying to find a "cure" for ageing.

They include Jeff Bezos, the world's richest man, who has pumped money into Unity, a California company that hopes to stop the ageing process.

It's already raised over $116 million in funding and is trying to find a way to block cells that cause arthritis and loss of sight.

Paypal founder Peter Thiel has also ploughed cash into Unity having spoken about finding a cure for ageing for years.

"Most diseases are linked to aging," Thiel said at Web Summit in 2016.

"You have a one in a thousand chance of getting cancer in the next year at age 30, you have a one in ten chance of getting cancer in the next year at age 80.

"So we definitely want to find a cure for cancer, maybe if we find a cure for aging we cure cancer along the way."