well, so far I have done a test with it: I winched my brother's 99 Montero up a steep grade the entire length of the cable and it showed no signs of slowing down.

but doing some math, we can estimate about how long it would last me:

Here is what the winch draws:

2000 lbs 145 amps
4000 lbs 185 amps
6000 lbs 230 amps
8000 lbs 270 amps
10000 lbs 315 amps
12000 lbs 370 amps

so with my 105 amp hour battery, I can winch for these lengths of time:

2000 lbs for 43 mins
4000 lbs for 34 mins
6000 lbs for 27 mins
8000 lbs for 23 mins
10000 lbs for 20 mins
12000 lbs for 17 mins

hows that for a calculated answer....I think I will be good.