If you use the survey module and see that it is empty you can manually stop the cycle and move to the next asteroid.
This manual switching of the rock benefits you, the active miner, over say the braindead bot or massive multiboxer, as you can increase your efficiency by not wasting time on an empty rock. I don’t know for sure, but I am pretty confident this is even intended to give survey modules a more useful purpose and allow active players to mine more efficiently than someone who is mostly AFK. I mean, if CCP wanted, they could just reduce the cycle time to a few seconds to prevent any wastage.
If you want a countdown timer you can build one yourself, or just use your watch. In fact, I think people have even done so in the past… yes! like this one: