Dfgt seems to be a little problematic, I have one too. I have to go into the wingman software, onto the Global settings page, change the wheel rotation to say 899° and back to 900°, click Ok before I start AC from Steam, or the game will start with the wheel in 360° mode 
edit: I too only power it up (and thus calibrate) when I want to play (I built a switch into the cable)
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edit: I too only power it up (and thus calibrate) when I want to play (I built a switch into the cable)