I'm torn though if I should keep charging it and just do the mountain mode for my work commute, I estimate that my battery will deplete enough for mountain mode to trigger the engine when I'm about 7-8 minutes from home so at that rate it might take a few weeks to burn a significant amount of gas. It should stay warm enough for the next week or two that I won't get ERDTT too often, but I'd hate to get caught out somewhere with no battery if the ICE has another episode.
I wish there was a way to trigger the engine to run when the battery was full, that way I could run the gas all the time but still have battery in reserve in case I need it.
Sounds like your daily commute is just a bit beyond a full charge distance (when you switch to Mountain Mode, your 2012 Volt switches to gas about 7-8 minutes from home during the commute). That suggests if you drove the entire commute with the engine running, the drive would consume about 4 liters of gas for each commute, by my rough guess.
You could do that by switching to Mountain Mode during one commute, and then not recharging when you got home. The following morning, the battery should still be charged to that ~4 bar level. If you then immediately switch to MM as you start off, it’s similar to using Hold Mode at that level... you could drive your entire commute with the engine running (and still have 4 bars of power in reserve in case you needed it). I use this technique on long road trips in my 2012 Volt to keep that extra ev in reserve in case I guess wrong on my need to stop for gas.
It’s a little unclear how the Gen 1 Volt system would respond to driving with the hood unlatched. When I pop the hood on the 2012 Volt I’ve been driving for 9 years, the smaller motor MGA draws some power from the battery to start the engine, and then the engine cranks the generator long enough to replace that power (plus a little bit more), and then stops cranking it. The engine continues to run as long as the hood is open, but after the first 10-15 minutes, no more charge is put into the battery. One person on the Facebook Volt Owners page did manage to charge the battery all the way by turning the car off and on and off and on, each cycle adding that "little bit more" until the battery was nearly fully recharged.
IOW, if your drive your Gen 1 Volt while the system thinks the hood is unlatched, the engine should run and use gas for that purpose, but I don’t know if the extended range propulsion configuration would be engaged, using additional gas to crank the generator. Perhaps the system would continue to propel the car using grid power from the battery until the charge had dropped to the normal "switch to gas" level.