Do game cards add onto other cards or overide them??
 

I want to buy more than 1 game card(1 month ones). Lets say I bought 3 and put all 3 codes each at a time but on the same day...would that mean I have 3 months or do they cancel each other out?? answers would be much appreciated, ty :)

I think they sell year membership cards for less than it would take to do that.

I would think that they'd just add onto the existing membership as that's what happens when you change your subscription option. You may want to contact Disney's billing department for a firm answer though.