How to combine multiple licenses under one 3-device account?

I wanted to share the outcome, publicly, in case others have the same issue:
 
A Webroot rep was initially helpful and sympathetic; my request made sense to him, and he said that after I installed my newly-purchased 3-device license, he would extend its expiration date to reflect a *partial* credit for my 5+ years of unused time remaining on various Android devices. I never expected to get full credit, so I thought his offer was fair.
 
However, a day or two later, the same rep informed me that he had overstepped his bounds. One of his higher-ups explained to him that licenses sold through Google Play fall under different "budgeting" (his word) parameters. So, in short, he retracted his offer: I get no credit for unused license days.
 
Thus, the lesson learned here is that Webroot is unwilling (they would probably claim unable) to combine existing licenses under their newer 3-device and 5-device subscriptions.
 
The strange (and dumb) message to users is, Don't buy anything from Webroot until your current licenses expire.
 
This is not to bad-mouth the software -- it is still (imho) the best. But the people running the day-to-day operations really seem to be short-sighted, putting a higher priority on accounting budgets than on long-term customer retention.