This question got me thinking Transient RSS feeds in wp_options not removed automatically?

Transients are supposed to expire and be deleted. However the only way I see this handled is when transient is expired and requested, then it is deleted during request.

What if transient is expired but never requested after that? From description in Codex I thought that some kind of garbage collection is implied. Now I am not so sure and can't find any code that performs such.

So will it just be stuck in database forever?