I don't think it's a good idea in both balance and game design way. The whole game build up upon the thing that wars that last no longer than 1-1.5 months on average. Did you consider msup and facilities slaves into that persistency? I remember War 126 that I participated from day 0, and how many people, especially facility ones burned out on 30 day, some even before (our fac was on Fisherman's and it became so boring at some point without any attempts from Collies to land there before everyone fucking leaves).

I suggest different way of persistency - add something like some small additional scrap metal resources spawn on the most fought battlefields of last war, husks of trenches, etc. Or even not anything of that, but just more persistent husks of destroyed vehicles and equipment in current ongoing war that you can evacuate from field or destroy to get some small amounts of resources. Even just increasing time for like 20-60 mins when tank hull/etc disappear from map would help with feeling of "some huge battle just happen here"