The batteries that came with my airstyle didn't last more than a couple of hours (the first night I played it several hours straight to see if I'd be satisfied). After about 3 hours, I trashed those batteries & switched to my rechargables.
Before I go on though a short note here: I love NiMh rechargables. I've been using them in digital cameras & other devices for a couple of years. They are the reason I don't mind buying a wireless mouse or a wireless Airstyle. Once I've bought them, that's it for batteries for a few years.
So to me, the 5 hour life of a rechargable battery is fine. I swap them out with the others that are charged and go on playing.
Perhaps I should note that the 5 hours time average for me is not that the device stops working. It is just that after 5 hours I start to notice a lag. Not a big deal on a game like ICO, or even MOH: Rising Sun (in most situations) but in the game I've been playing most often, TAA, it is murder.
So I probably could have gotten another few hours of play out of the batteries before they became unusable on most games (maybe even another 5 hours). But since I've got a ton of rechargables there is no need for me to do that. I gave my review based on the way I play my games & the responsiveness I expect from a controller.
Finally, I'm running the Airstyle in normal Analog mode with the Rumble turned off (the default setting). The instructions that come with the Airstyle show an unrealisitc battery life chart. I think 50 hours was if you played in ECO mode (not a responsive) for good alkaline batteries, and 30 hours in ECO mode for rechargeables.
I've not used ECO mode, so I can't speak to that. I've also not used good quality alkaline batteries (Duracell, Energiser, etc...). I've used decent quality NiMh batteries and have been satisfied with the results thus far.
I suppose it all comes down to how often you play & what's important to you. I own a small condo & use my PS2 as a game machine & a DVD. Since my condo is small, I didn't want wires all over the house so I opted for what the reviews I read said was the best wireless controller for the PS2. I've got the money to spend on the controller & the rechargeable batteries.
So perfect for me, but for those on an allowance or tigheter budget (I remember those days when I was in high school working at restaurants), maybe not right for you.