Why would you do that to begin with?
Maybe if the Dr. is backfield for a full rehearsal setup and the drumline happens to be placed on the back sideline, or something similar? You shouldn't really be 4 feet away from the Long Ranger with it cranked like that.
It most likely wouldn't have any long term effect as long as you aren't doing that everyday
Depending on the decibel level, even half an hour is enough to cause long term damage. However:
i mean without earplugs or anything.
The drums you're banging on for several hours at a time every time you rehearse are doing a lot more damage to your hearing than the dr. beat. Get some earplugs!