I've had a i730 for over 2 years and I really love it. I had an extra phone so I gave it to my Father-in-law.
On several occasions the phone has gone from 100% to 30% in a short period of time and the battery dies shortly there after. I suspected a bad battery so I replaced his battery with an extra.
He was on vacation and experienced the same event with the new battery. Upon his return I exchanged his battery for mine and booted up his phone. I can't find any problems (ie apps running in the back ground, BT or WiFi on or anything else) I'm wondering if the problem is with the phone or the battery. I did order some new batteries.
Any ideas? I'm thinking of doing a hard reset and reloading all the programs.