How often should I spin?

I have just started spinning in an effort to break through a weight loss plateau that's been going on for a few months now. But I'm wondering how much is too much? Was thinking I'd go 3 days during the week plus one at the weekend, but don't want to do myself injury either.

Have to say I love love love the class, just need to get shoes with a thicker sole to stop my feet hurting!