2.3.5 was best battery upgrade I could buy
Upgraded to Android 2.3.5 (Samsung Galaxy (Fascinate)). When I first got the phone, I was on 2.1 and had to charge the phone every day (1500mAh stock battery). This improved when I went up to 2.2.x and with 2.3.5, I need to charge it every 2 1/2 to 3 days. My wife has the same phone but I bought her an aftermarket 3300mAh battery. She goes from Monday to Friday (casual use only - but never turned off) on one charge. This is NOT 4G which I'm sure would kill my battery at the least.