By “reusing,” do you mean repeatedly using one location to store a variety of information temporarily? Like a weekly grocery list or, in your case, a new lecture every other week? Or, do you mean storing different kinds of information in the same location permanently?
I’ve done the former back when I was experimenting with playing-card memorization. For me, it didn’t work well; there was too much “ghosting” from one trial to the next. I think that would have been solved if I’d had several “standard” palaces that I rotated through as I was trying to memorize cards; in theory, by the time I was back at the first palace, the cards I’d put there would have vanished from my memory completely and I could use it fresh. If that’s the kind of “reuse” you had in mind, I might suggest starting there, with a couple of palaces you rotate through. You may not need them all; you may be fine reusing one location over and over again. But if you do need them, you’ll have them.
I don’t really recommend the second approach, especially if you’re just starting out with memory palaces or the information you’re adding is in any way similar to the information you’ve already stored there. (I think it could get confusing to distinguish between the images.) That said, I’ve never tried it; those who’ve used it successfully may have some recommendations for maintaining some kind of division between the layers of information they’re storing on top of one another. My only suggestion would be to make sure the subjects you’re storing there are as different from one another as possible, to make it much easier to keep each set of images distinct from one another.