Don't buy thinking you'll resell them at full price in a few years - that's over. The market is definitely saturated - huge production runs, variants on top of variants, and people are getting tired of them. The discounts you see everywhere aren't random; they show that the initial hype has deflated quite a bit.
That said, if you actually love them and want them for your personal collection, the sentimental value hasn't gone down at all. The important distinction is between financial investment and passion: as an investment they don't work anymore, but as a hobby they're totally sustainable. The lines that still hold value best are ones tied to franchises that are still relevant (certain Marvel chapters, Star Wars for true fans, some rare exclusives from the golden days) and genuinely limited editions or ones with printing errors. But we're talking about holding value, not making a profit.
I'd keep going if I liked them, but with a lighter mindset. Accumulating just to fill shelves hoping for a financial return is silly at this point, but having a curated collection of pieces you actually love is a whole different thing. Maybe instead of always buying new, just get the ones that really make you laugh or that represent something you actually care about. Your 80 pieces probably tell a better story than 200 bought just for the sake of it.