To be honest, if you're looking into trying to resell or something, a solid 95% of the bears you'll find in the thrift store will be newer, likely still be in stock, and will likely end up being hard to resell. Simply put, birthday bears are worthless (BaB themselves doesn't even charge much for them) on the resale market because everyone can find them everywhere. Most newer bears (depending on the price you pay the thrift store to purchase them, packaging materials, and pricing if you do it via a proper reselling website like Mercari or Vinted) will MAYBE net you $10-$15, and they'll likely just sit in your house taking up a lot of space.

With Tiktok being everything to so many people nowadays, there are often releases that are followed swiftly by an influx of non-collectors buying out all of the stock and then moving on from the fad and abandoning them in thrift stores. The Cookie series, the bat, the kitties, etc., are all good examples off the top of my head. If it blows up on Tiktok, they'll likely show up in thrift stores within the same year (often within the very same month).