I try to only drop trackables in newer caches, or frequently visited caches. I hate seeing one sit in a cache for months at a time, so I try to drop it in one where it should be picked up quickly. Since I have it in my backpack, I'll "dip" it at each geocache I go to. You may also see people just "dipping" trackables at caches, because they're using it to log their personal process. I have a bug on my keychain, and I use it to see all the places I've been. It's nice to see the map of my travels.