Depending on how many cubic centimeters your tank is and how fast youe engine drinks fuel, it coult be as little as 4min or as long as 10min.

For example, an HPI Savage with a 160cc tank and a K4.6 (.28ci) engine will require about 11min to drink 160cc of nitro, assuming good tune.

Of course, a .12ci engine attached to a 160cc tank will run much longer, maybe 20min? I dont know, I never tried to put such a big tank on such a small engine.