I havent had any abnormal wear on my 645's so I am not convinced about the wear thing on metal gear servos..I think it might be over played....I have a bunch of DS 821 digital servos that I have had quite a few failures with though..Even cost me a plane..I dont know if it was because I was mixing them or not..I didn't know you werent supposto untill reciently..I think digital servos are fine but I just dont see the point because I can pretty much use my radio do adjust my servos for the kind of flying I do . And espially if you cant mix them and they use more juice...I have had no trouble with the Karb servos or the metal gear..Where is this info warning us against using karb servos in 1/4 scale..I am unable to find it..In fact I am not able to find any info on warnings about karb servos being too brittle and failing .. And I am not disputing the fact..I want to find out as much as I can..Believe me I do not want to lose one of my 1/3 scale Cubs to a servo failuer..I use a lot of 755's in the Cubs..I have never had any problems at all..They have huge ailerons and one servo per aileron .. I always figured if I had a failuer I would still have one to get me down however if I am using a servo that is not supposto be used in a gas plane , I should change it.. Where is this information? Thanks