It doesn't matter that the awning is powered by 12 VDC if the motor is geared properly . They make 12 VDC winches that can pull a 3 ton truck . I suppose if you ran the awning in and out 20 times a day you could drain your battery if you really tried.
I haven't noticed any detrimental effect to our batteries while boondocking. Usually a couple of times in and out a day are sufficient to satisfy my appreciation for technology and then I stop, maybe