Is it possible to calculate Lead Age, in real-time, keeping business hours into consideration?

P.S. I don't want a batch to update a million leads every hour.
 

I have thousands of prospects in my database that I want to start calling on. They are already contacts associated with Accounts. What is the best practice for this? Should I create an opportunity for reach prospect I want to call on and put the opportunity in the Prospecting stage, even though I don't yet even know if they need my services? I'm struggling with understanding the best way to manage a brand new sales funnel - before you actually know if there is a need for your service. Thank you!