You can get stuff with much better warranties, but expect to pay more.
There are different ways of selling the stuff.
Some places are mass discount brokers...you get the best price up front but it's yours for better or worse. A little more risk involved, but you can buy in bulk and just write off the duds.
Some places offer top notch customer service and will replace
batteries with few if any questions asked. Those places will also have higher prices. Here it's usually more about customer loyalty than written down policies. I.E. If you're always buying
juice and other supplies from a vendor, s/he is more likely to toss in extras and replace bad stuff no questions asked.
Some places try to strike a happy medium between the two models mentioned above.
It's important to remember that a single fat battery cost almost as much to ship around as it does to replace with a brand new one. Striking a balance between a good DOA policy and trying to warrant these things for longer terms isn't exactly easy. The vendor has to protect himself against fraudulent customers too. So 14 days for an inexpensive battery seems pretty reasonable to me.
Try some places...you'll find one pretty soon that does business more like you'd prefer. Just know that products with 'longer guarantees' will probably cost a little more or have some kind of strings attached to the stellar customer service.
An example of 'strings attached' customer service. SmokTip.com, and other similar mini-cig outfits will send you fresh
batteries, chargers, whatever you need for life at no extra charge, so long as you buy 'their prefilled cartos' from time to time, and don't get caught 'dripping your own liquids' into them.