The battery SHOULD be around 3.5 RESTING VOLTAGE . I sure wouldn't push it that long for the first time. If the current happened to be 5.2 then you may in fact pull it down too low. It might also only average 1-2 amps and last a lot longer. Usually what I do if I have an unknown discharge current is to time a few runs and then go by this chart as a "fuel gage" Most everyone uses 4.2 as the full mark, but some people use 3, 3.2, 3.5 3.6 3.7 as the empty mark and there isn't a lot of capacity difference between 3 and 3.7

Charge % Open voltage Mah

100.00 4.2 5000
90 4.13 4500
80 4.06 4000
70 3.99 3500
60 3.92 3000
50 3.85 2500
40 3.78 2000
30 3.71 1500
20 3.64 1000
10 3.57 500
0.00 3.5 0