Everyone who is saying 501 - do you mean 510? Just don't want this to be too confusing for people.
For the OP - why bother switching - you already can have both. Use KR8 batteries and you can use with either KR8 and Vapor4Life cartos OR attach the 901 atty and use 901 drip tip or 901 carts with that.
As for the longetivity of cartos vs atomizer (atomizers burn out too), I think a properly used and maintained atomizer has a good chance of lasting longer than 5 cartomizers that are refilled and reused until they croak. Cartos have a convenience factor though many take longer to fill than filling a cart. Carts can be more finicky than cartos (w/ getting the
juice and stuffing right) and have to be filled or topped off much ore often, but yes, unless heat and use stretch the plastic and make the cart too loose, you can reuse, restuff, clean with hot water, use over and over.
BTW - Once the white original stuffing is not working well, I switch my stuffing to blue foam. And you can actually buy precut pieces for 510/901 cheaply at
http://www.strictlyejuice.com/. I like it better than the white stuffing.
NOTE - if you have automatic KR8 batteries I do not recommend dripping with them unless you are really careful because the autos have a hole in the threaded end of the battery and if juice gets in there it could kill the battery.
I think I got mine here - good vendor and low shipping
http://www.litecigusa.net/DSE_901_s/56.htm
Get the normal atomizer (not the low resistance one), the aluminum or steel drip tip (because juice seems to get more stuck on the way down with the plastic ones), and carts.
I haven't got cartridges yet for mine but this is the cartridges section
http://www.litecigusa.net/e_cigarette_cartridge_s/34.htm
but I am not familiar with their liquids other than their Dekang which is the 100% PG Chinese stuff. You could buy your favorite juice from Vapor4Life (as a juice bottle).