Could just be a defective set of rings. Not feeling the ridge theory. A ridge will have a smooth transition not a hard edge and besides the oil ring is the lower ring, not at the top of the piston.
Oil starvation from one cause or another will shorten ring life. Running the right weight oil for the time of year is important. During a cold start up it takes time to get the oil to pressure up if its to heavy a weight, on the flip side the oil can be to thin when in high heat area or overheating takes place. Running real rich will wipe out the rings too as the unburned gas washes the oil off the cylinder walls and thins out the oil in general.
'05 4.0: G-Force T-5, MGW Shifter; VMP MAF/ CAI/93oct N2O Tun; CHE K-Brace & Torque Limiters, Rr Ctrl Arm; Shorty Headers; Centerforce Pressure Plate, McLeod DF clutch, Adj Slave Cyl; 8.8" 4:10's w/ T-Lok; Coast Alum D/S; FRPP Dual Ex; 18" Bullitts; CF Hood; Rr Louvers; SS Gen 1 Frt Cover. ZEX N2O - 100 shot bests: 1/4mi ET 13.495/MPH 103.95 (*only mods were VMP N2O tune & CAI; shorties w/ duals; t-lok).