250 ma per servo? where did you find that? The spec is for @ 7.2 ma per servo at idle which is the position servos spend a great deal of their time in. The higher currents are usually measured in a "stalled" or highly loaded condition which you try to avoid by proper setup geometry. The throttle is the one control that may spen a lot of time at an end point and therfore you need to make special care to make sure doesn't bind at the ends. The other controls should travel freely to/from their end points and usually spend very little time at the endpoints so they will not draw high currents for an extended period. Digital and High Torque servos do draw more current and require larger batteries. At a VERY rough guess, your entire system MIGHT draw 100-150 ma during a high spike of normal flying. 3D being a bit higher.