My 3gs running 3.1.2(7d11) & firmware 05.11.07 is unlocked with blackra1n a few yrs back. I wondering if there is a newer/better option to unlock/jailbreak. I dont like to the idea of worry about battery shutting down and locking the phone.
Go get iDetector and see if you have old bootrom. If so you are all set. If not then come back in a couple more days for recent updates, or you could deal with being tethered as you seem to be used to it.
You will not loose data just by going into DFU mode. To get out of DFU mode, just hold Home + Power button until phone turns off. Then, you can just reboot normally by pressing the power button.