Do they sell cartomizers for the Joye EGO? Do they replace cartridges? Are they as easy to refill? How long do they last?
When you're looking at cartomizers, you'll notice that they are identified by a number like 510 or KR808, etc. That denotes the connection type. Your Joye eGo uses 510, which is the most common. That gives you a very wide field to choose from!
Since it's an eGo, you can use the EMDCC as gramva mentioned (without any adapters or anything). Those puppies are awesome. Once you have settled on a juice you like, trying an EMDCC is one of those things you just gptta do. Make sure it's a juice you like tho, because the carto holds a LOT of it, and you can't really 'empty' them to switch juice.
So to answer, yes, any carto thats a 510 is fair game for your eGo. A cartridge goes on an atomizer. The cartridge has the liquid, the atomizer has the coil. A cartomizer combines the functions of the two in one unit/piece. So it will replace the atty and the cart.
Refilling is a breeze. When you first fill a carto, you will be popping out the little plug on the end. Actually, your best bet is to toss that anyway and put a drip tip in place of it because the carto can get a bit warm, the drip tip makes it more comfortable, especially if you chain vape a bit. Also easier to remove/replace than the stock mouthpiece plug thing. Whichever you use, refilling is a simple as popping the plug or tip off and dripping the juice into the absorbent wadding inside the carto.
How long do they last is hard to answer.
Between refills? That will vary depending on which one you go with - some have larger capacities, and there's the EMDCC previously mentioned, which will hold a bucket of juice. (OK, bucket is a SLIGHT exaggeration). Also, how long will depend on vaping style. You may find that a standard Boge lasts you all day, while someone else who vapes heavier might only get half a day out of it. Sort of like saying, "How long will a can of Coke last?" Answer is different for everyone.
How long will it last in terms of lifespan? That is hard to nail down as well. I have some that I have used a lot and got about a month out of them, whereas others have only survived a week or so. Sometimes it's the carto that decides lifespan, sometimes its a particular juice that's rough on them, and sometimes it's the user and their style that will decide.
As for catro's tho, you can get 15 Boge carto's for twenty bucks. As you can tell from that price, they are meant to be disposeable - but they're certainly not single-use.
(( and I bet you thought those were simple, straightforward questions with black & white answers... LOL ))