Yes, NIMH batteries are not smart batteries like some Lithium but good chargers don't use time to determine when charging is complete. The good charges like all the fast chargers use charging IC that are based on delta V and delta T (voltage difference over time and temperature difference over time.) Temperature is not always practical for separate cells so they rely on the voltage change over time. Battery packs (like laptops use) contain thermistors that are feed to the charging IC to provide the delta T input.
Trying to charge a fully charged battery will slowly over charge it. But since the IC is able to detect this condition the charge should stop in a few minutes. As long as the battery is completely cooled down before attempting to recharge and you don't do attempt this like 20 times in a row no damage should be done.
NIMH batteries don't need to be drained completely to avoid memory effect. You just have to fully cycle the battery once every 30-60-days and any temporary capacity loss will be undone. Always draining a battery before charging (like letting a disc play and not listening to it) will prematurely wear out your battery.