What's the useful life of Ignition version 7.9 and 8.3? I'm told by my 3rd party integrator that 8.3 will by unsupported by 2030.
For ongoing system health checks and emergency support, is it most effective to source through Inductive Automation or a local 3rd party?
v7.9 is already completely end-of-life.
See the schedule in this blog post for more:
8.3 will be supported until ~September 2030.
Before that happens, the next LTS version will have been released, 2028-LTS.0, in ~March 2029.
Whichever you prefer, but in either case you should maintain at least BasicCare support, to get the upgrade protection.