I'm assuming that you mean Job Centre Plus (JCP) and not JSA (which may mean Job Seekers Allowance)? If so then the answer is no there's no time limit as it appears to vary from region to region this is despite a 13 week assessment phase which doesn't appear to be getting stuck to by all regions.
You can of course call the office dealing with your claim and ask them where your claim is in the system.
Nothing on this board constitutes legal advice - always consult a professional about specific problems
Yes you are right it is JCP (doh) my mistake and my original claim was made at the beginning of April I had my medical on 22.07.10 and still no decision still a stressful time waiting for results and planning where you are.