This is a great point; I wish I had mods points. While the issue could be kept to a minimum by keeping the gas tank small 4-5 gallons& keeping it between a quarter and half a tank a lot, but if you ran for a year without engaging the engine because all you drive is a few miles a day, you may have a serious problem. Most hybrids up to now this hasn't been an issue because they run their ICE a lot, with the Volt, it might start to become a problem.
Should be interesting to keep an eye on this topic.