I kept a cactus for a long time, through all of college, while I was staying at my parents house. It was a tiny little thing that I figured was only barely hanging on, but I at least tried to make sure it was watered and so on. After I moved out after graduation I left it there and my Mom tried to find time to take care of it every so often. Apparently it got in pretty bad shape so my brother took it off her hands and repotted it.
I figured it was long since dead after I moved out. But last I visited around the holidays I saw it at his place and didn't even recognize it, it had gotten about twice as tall and had new growth!
I was pretty happy to see it was still kicking, as funny as is it to care that much about a cactus, I think I'd have been a little sad to know it had just dried up and died.