Those attys can last for ever if you look after them. They are 2.5 ohms (I just tested one) although they can go down to 2.2 ohms. That means they put out a lot of power on 5 volts. They can't 'go off', they can get burnt up or die off though. If you don't keep them
very wet they can burn, resulting in a burnt taste that is hard to get rid of (needs strong cleaning). However, excessive cleaning can make them die off.
The best way to use them is: don't work one atty until it dies - rotate them. Use 3 or 4 throughout the day, mine have lasted for over a year doing that. And keep them really wet. That means you will need some sort of cart mod, the original fluval filler batting is only used because it's dirt cheap, not because it works well. Blue aquarium foam is good, or one of the zero-filler mods. I only use RYO cig filters, specially cut, in my 510 carts now - and they work fine with VG on 5v or 3.7v.
Don't flog the guts out of your gear, treat it right and rotate it, and it will last. I laugh when I hear people say their attys last two weeks. I'd feel robbed if they only lasted two months
On 5v you don't need to clean atties unless you are vaping fudge - the power burns off all the gunk. Don't do dry burns unless you are trying to revive a near-dead over-cleaned atty. Cleaning and dry burns take life off an atty.
