Lumley, who recently starred in the Absolutely Fabulous Olympics special, told The Mirror that she and co-star Jennifer Saunders could continue playing Patsy and Eddy "forever".
"We've already flashed to a time when Patsy's drooling and propped up in a wheelchair with a drip attached to a vodka bottle," she explained.
"Her and Eddy were about 102... No matter how badly Jennifer and I decay, we could carry on playing the characters forever [and] June Whitfield [Eddy's mother] seems to be getting younger all the time."
The 66-year-old actress also confessed that she shares some traits with her flamboyant, chain-smoking character.
"I only have maybe five a day," she said. "But playing Patsy has put me in a cage that makes me look like I smoke like an old wizard.
"I drink a fraction of what she does but I'm a bit like her. I don't have her vicious language but I adore her."
Lumley revealed that she has also managed to accumulate wardrobes full of clothes and accessories while playing Patsy over the past two decades, some of which she plans to auction off later this year.
"I'd often buy Patsy's clothes from the BBC at half price because I loved them so much," she said.
"They're iconic pieces that Patsy wears on the front of the DVD box set - I know which outfit was worn in which episode - so I'm hoping someone might like them."
When asked whether Absolutely Fabulous is likely to make a more permanent return to screens, Lumley said that it is very much dependent on her co-star's schedule.
"[Saunders has] got so much on her plate at the moment. She's super-busy with the Spice Girls musical Viva Forever! But she works fast so hopefully next year she'll start looking at Ab Fab.
"I've sent her one or two emails to remind her. I'm hoping that a light lash of the whip will keep her motivated."
Watch Joanna Lumley talk about the Absolutely Fabulous Olympic special below: