I have had my Tucson PHEV for over a year and still don't know the optimal strategy for charging it. I would like to achieve the greatest MPG, maintain the health of the battery, and maintain the health of the engine. I could charge it daily or every other day when there is less than five or 10 miles on the battery, and the engine would never engage. Is it OK for the battery not to totally discharge before being recharged? I could deplete the battery every three days or so and allow the engine to run for several miles before recharging. I could do a combination, allowing the engine to run every several weeks or so but otherwise going exclusively as an EV. Any solid information on this?