Two to three weeks is normal for a disposable clearomiser, which is what the CE4/stardust is. You could try a CE5 which has a replacable head and they are generally better quality.
A disposable that last 4-6 months in constant use is unthinkable, and even if you only use it in rotation is well past its us-by date. Are you finding the taste is going off after about 2 weeks? That's the juice caking and burning on the coil. The next step is that usually the brown colour will backwash into the tank and taint the juice.
I think that what is happening is that your tastebuds are coming back. It was always starting to taste nasty after two weeks, but now you can tell the difference. The taste thing seems to be different for everyone; some people get it back in 6 weeks, for others it can be 9 months until they notice a dramatic improvement.
The type of juice will also affect the life of the coil. Thicker, darker juices will clog up on the coil faster, as will high VG juices.
I can also recommend the Evods. They are bottom coil devices and work very well, and have replaceable heads. I recommend you go for 2.4 ohm heads for replacements as it sounds like you're more into no hassle/minimum fuss more than anything else. Lower ohm coils will run hotter and need more regular replacement.
2 years is a good life for a set of batteries. You should probably think about getting some replacements for them soon, but I don't think it's the source of your problems. Old batteries will just need charging more often until they eventually don't hold a useful charge.
ETA: It strikes me that you might only be a very occasional e-cig user, which might explain the longevity of your CE4 clearomisers. There's an awful lot of cheap copies of these on the market now and the quality of some is questionable (
but you can get a pack of 10 for less than $15). Leaking and badly made coils are common with the cheap stuff I'm afraid, reports of one or two DOAs in the pack are not uncommon.