I have yet to plug in my 08' it gets parked on the drive and starts regardless of the temp. we had a 3 week spell in december where it didn't get above -30 and dipped below -45 and actually hit -51 over night. I use synthetic oil which makes a huge diffrence, and keep an eye on the batt.
08' Jeep Wrangler
08' Dodge Avenger SXT (winter beater)
64' Plymouth Sport Fury(sold)
58' Triumph TR-3A(in 1,000,000 pieces)