The Q701 which I presume is very much like the K701/702 hence there is no set amount of time for burn-in, some people will say 100 hours, 500 hours, 1000 hours etc... It's all very subjective in my opinion, I usually just listen to them and find out that over time the sound usually smooths out a bit or that is at least what I perceive, the difference in the end will be a minimal change at most, so don't believe the OMG after 100 hours the headphone sounds completely improved in every aspect, that is pure delusion
. If you want the Q701 to have a more smooth, natural and lush sound you have to look into proper amping and source. This will bring you closest to achieving your desired sound, if you are not satisfied after the "burn-in" that is...
Cheers,