My Joytech charger has never had any problems plugs in to the Wii's power slot then plug the wii in the the back of the chargers plug.

Funny thing that this topic is made today since Nyko Remote Charger was reduced 33%. This would be a perfect time for anyone with a Wii to pick one of these up as they are in fact awesome.

 This is quite common with old batteries. Typically rechargable batterries can last ~1000 charge cycles, or 1-2 years worth of use. I've been using the Energizer 2500mah for 1-2 years and they still work great, but the oldest ones are starting to drain faster.

 The only problem i have is if i drain all 4 sets i can only charge 2 sets at a time.

I turned the rumble off on mine (rumble is so last-gen :P ) and my standard AA batteries have lasted forever...

 Yeah, I also turned off my rumble. Never cared for it, and now that the remotes are wireless it drains em faster.

The weird thing is that they aren't old at all. Got them early this year, and they're supposed to be really high quality ones, so I suppose I just messed something up. =/ 

depends how much you have charged them up (and some batteries wont work well with certain chargers)
If you have not charged them many times, and definately have the right charger then i dunno,... what make are they? how much were they? and what mAh are they (more means they last longer....but i have some 800mAh that last longer than 10 hours on LoZTP, although if you leave them around for a week after charging they lose half the power....which is why i bought these Hybrio things because they said they dont do that. And it must be partly true because they come in the packet pre-charged.

some chargers will overcharge a battery, which can destroy the battery. Also letting the battery fully discharge before charging again extends the lifetime of the battery.

If your charger doesn't have protection for overcharging and leaking, and doesn't drain the battery before charging i would get a new one. I got the pack of 4 batteries with a decent charger for ~$15. I'm thinking about getting one that is capable of 8-12 batteries with all those features, but it can get expensive.

If I can find a charger for $20 at a retailer, I'll definitely get it...I just couldn't bring myself to get it for $30 I guess.

 Suppose I should have put the price in there, but Amazon is selling the Nyko one for $20.