o2 sensor MADNESS!!!!!!!

Hi, got a 97 G-10, 4.6, Started having problems with rough idle & hesitation, had complete tuneup...no help....finally code : high voltage bank 1 sensor 1, changed it problem gone, for 1 week! symptoms back, new code: high voltage bank 2 sensor 1, changed it problem gone for 3 days!! symtoms back, new code: high voltage bank 2 sensor 2 WTF!!! These o2 sensors cant be going all bad at once can they??? High voltage means running rich, right? maybee the puters going bad??? I don't know but at $55 a pop & bloddy knuckles to boot, this really bites!!!!! Any ideas would be much appreciated.....thanks....T