I guess I will try to answer..
It would depend on what you have in with them. Air stone, I wouldn't let them go for more that 24 to 36 hours. Filter and some water changes/chem additions, maybe 48 hours plus.
I have 4 pep's that I no longer want in my tank. I told someone I had these guys and that I was getting rid of them. althou I do not have any where to put them other than a 2 1/2 gallon tank. so thats where they went. if this person doesn't contact me by tomarrow. I must find these guys a new home. I have 4 large peps. I threw a very small power head in the tank. I am wondering if they would be ok i my fuge? my fuge has large hermits in it.