It's a wise thing to do if you've just moved home to a new area that's unfamiliar to the cat, it won't get lost so easy. It'll have put down it's own scent and understand the scents of the new environment, other cats and things. It's a lot of information for the cat to process. Once you think the time is right, let it roam free if you can. As for doing it on a regular basis, yeah whatever, I don't see the problem apart from meeting chavs in the streets with their inbred abominations. That could get nasty.