Not sure how often you could do it without building tolerance, I used it maybe twice a week for several months, that definately caused tolerance. None of the 2c's I've had seemed to degrade over the year or so I had them, all were stored in original bag, room temperature. I noticed serious change only in 5meo-dmt, though other tryptamines likely do as well. From everything I've read 2c-anything should be stable almost forever. Different source, though I've heard they get it from the same supplier.