i have the same issues...i buy the ultras and they dont last 2 months...i buy the plain ones..they last a lil longer maybe a month more tops...i thought about it being the connectors, but havent gotten around to trying to replace them..its hard enough to get my hands in there to do them damn...
i just did a full tune up on my 2003 protege 5, 130k. plugs shot, and wires fell apart pulling em off..ran great up till about 3 days before i got the tuneup..started sputtering and missing a lot..
im so ashamed...lol....and they were all original parts...