In 2013, Yahoo had announced that it will delete inactive accounts and free them up to give them to new users (recycle account IDs). Users could apply for the ID they wanted and about a month later they would know if they got it or not. I think there was a fee for that? I don't remember that.
Is this policy still enforced? Are inactive accounts deleted and recycled? I attempted to find but 2013 was the only year that was mentioned everywhere and the language suggested that it was a "one-time" thing.
Edit: This page really confuses me. They say it is not possible to reuse permanently deleted IDs but everywhere else (including on this site) I find that in 2013 at least, they made it available for reuse?