I used to work in a shop that baked expiration dates into their license keys. The intent was to get customers that decided to go off of support back on it. Basically, the license key would be programmed to expire and when it happened, and they'd call customer service for help. Since they weren't on support, they had to talk to a salesman (and usually sign a support agreement) before they could get meaningful assistance.
With that in mind, I wouldn't recommend going off support while continuing to use the tool - either buy in for another year or make a clean break from it. Going off support means no more access to patches or service packs, and no help from HP when troubleshooting things that the patches don't cover. You don't want to miss a delivery date because the tool broke down and couldn't be restored in time to salvage the situation.