Well it seems he gets tired of his pets too soon...

I'm glad. It's not like he committed a crime or anything. In addition, no one knows the real reasons why he passed his former pets over to his acquaintances (many of whom apparently posted pics of those animals healthy and happy in their current homes). On the show, he mentioned he moved almost every year for 15 years and lived in everything from a half basement to the rental house we see on the show. From the show I think he gets lonely and the pets keep him company. I think it would be sad if he deprived himself of having a pet-companion because he couldn't absolutely commit to always being able to keep that pet for the entirety of its life. Stuff happens. Not all buildings allow pets. Maybe he couldn't afford them for a stretch. Who knows? Why does everyone assume he just got bored of them?