The 'Obviously' hitmakers think the band can keep going until they're 65 and plan to cash in every couple of years with a new tour.
Tom Fletcher explained to Top of the Pops magazine: "I can't really do anything else! I think we could do a tour every couple of years and make some money!
"I bet we'll all still be jumping around on stage then. I reckon we're the kind of people who will get to our 50s and will want to start getting really fit and healthy."
Harry Judd added: "I think the limit will be around 65."
The boy band reckon their secret to success is a genuine friendship and think their mutual support has enabled them stay in the music business for eight years, namely helping Dougie Pointer through his stint in rehab in 2011.
Harry explained: "I think it's because we're genuine friends. We take it seriously, but we have fun, too. And we're too scared to do anything else!"
Tom added: "So many people go off the rails, but when we do, we go off the rails together."
Dougie chimed in: "And then together we get each other back onto the rails."
Tagged in Dougie Poynter Harry Judd Mcfly Tom Fletcher