That is a concern. I am a happy driver of a Chevy Volt, and in daily commuting only ever use battery. The practices I use to preserve gas in the tank for long-term storage are:

* Keep the tank full of gas: air space is prone to condensation

* Avoid ethanol-added gasoline, it's more hypro-philic

* Add a fuel stabilizer (like 1 fl oz per 5 gallon)

* live in California, it's really dry.

These are adapted from techniques for winter storage of cars.