I have. Back in the day, where I was paranoid about mixing powders of different lots, I would dump the dregs out in the yard. Likewise, when I decided I was done with my can of H4831, which did NOT work well in the .348WCF, I just dumped it out. A few years later, I would regret that... because I could have used it in the 6.5CM.
I'm dealing with unwanted powders, now. I bought some different powders during the Obama shortage, namely TiteGroup, that I'm forcing myself to use up, and some test powders for 9mm and .45ACP... which, again, I'm forcing myself to use up. Waste not, whatnot. I've got partial cans of SportPistol and W244 I'll burn up in the .45ACP, then I have 2.5# of WST to use. 9mm gets the TiteGroup...