Stable Windows 7: Please stop inccessant upgrade reminders?

I have an extremely stable 64bit Windows 7 PC and I am choosing to NOT upgrade to Windows 10 for several months.  I have some in-house software that we haven't tested on Windows 10 (currently 21 CFR Part 11 compliant on this Windows 7 machine).  However, I'm getting an intrusive "reminder" to upgrade my Norton 360 (about once an hour) and while there is a "remind me later" toggle, the reminder come back way too frequently.  Does anyone know how to turn the reminder off?