I am using duracell 2300 mah ni-mh rechargables, I get about 8 - 10 hours use if i dont have the volume up to high, They also come in a combo pack with a 15 min charger for about 40 dollars, I have gotten about 50 - 50 charge cycles out of them so far with no noticeable loss of capacity. And they dont seem to self discharge a whole lot over a week of the scanner not being used.
I use the quick charger to charge them most times and get 8 - 9 hours using the scanners built in charger with the timer set to 24 hours i seem to get about 9 - 11 hours of use.
Ultimately it comes down to your usage of the scanner .. daily use on just batteries I would get a few 4 packs of batteries and the quick charger combo for about 70 - 80 dollars which is what i did
If your using your scanner alot on then power adapter and on batteries for a few hours or so and going back to the power cord just get 2 packs of batteries and alernate them once a week and you should always have a charged scanner thats ready to go. I have done this kind of use with my scanner as well for a month or two and seems to work well.
One thing i did notice is that using the backlight really drags the life down, even just the indicator led being on drained the batteries noticeably faster.
Again this is only my personal experience and both setups seem to work well for me.
I am trying some Energizer 2450mah batteries in my digital camera and they seem to last quite a while in it, I will try them in the scanner sometime soon and see if theres a noticeable difference between the two different brands.
One thing i will say is dont buy the rayovac rechanrgeables i only got about 3 - 4 hours most times out a chanrge with those. they are pretty cheap for NI-MH rechargeables for a reason.
Again this is all personal experience over the last year of having my pro 106 on a mostly the local motorola 800mhz trunked system, I dont know how the battery is on mostly conventional usage. But I hope you find this helpful. ... Of course if you find the solutions I suggest dont work well for you I think you can return the batteries to Walmart within 30 days.
Best of luck.