Short story to advice you:

Yesterday, tumblr staff dediced to suspend my main blog. I was hoarding five URLs unused and they just decided to deactivate it and made me delete all my unused URLs. I was using one of them, not posting stuff but using it with other purpose. I explained the staff why I couldn’t delete it, it was important and they gave a shit about it. So yes, I had to free em all and now I got it back, but they will take it away if I want one of those urls back, including the one I need.

Moral of the story: Don’t hoard too many URLs or they’re gonna fuck you up.