Escalation Intervals

Looking to have  Escalation Interval  have a Final stage Interval

I want to have multistage groups that get a short amount of time to solve a problem each.  and then a final stage that i can set a different Longer interval. 

I want to discourage them from acknowledging something they are not able to work on yet, and still get a notice until it solved.

right now one interval for all stage escalations isn't enough.  So either a time for each stage, or a additional time for the final stage.

Thanks.