Tier 1 VISA Expiration - Timeline for Employment

I was awarded a Tier 1 VISA in July 2009, but due to family circumstances I was not able to move to the UK until this Spring 2010. My Tier 1 VISA is good for 3 years, but I wonder if there's a rule about how quickly you must get a job and use the VISA.

Does the Tier 1 VISA expire if not used within a certain time frame? Any insight?

Thanks!

Technically, you can enter the UK on the last day of the entry clearance visa. But for practicality's sake, you must be able to show you've maintained or improved upon the original requirements of the visa in order to renew it and remain (income, etc.)

For instance, if you had to prove you earned the equivalent of £20,000 during the previous 12 months before qualifying for your original visa, you will need to prove that again.

In your case, entering this spring is fine, however, your "3-years to renewal" clock starts then and you'll need to renew twice to "catch-up".

P.S. My DH and I entered 3 months after our original visa date.