About 2 1/2 to 3 yrs seems to be the life of MSD 6AL boxes. I went thru 2 of them in the 6 yrs I ran my car. First box I started losing hi-rpm revs like my timing was off or I had hit the limiter. The second box started going in the mid to upper rpm range after the car had been run for awhile after start, an intermittent problem. Sent both boxes back to MSD and had them refurbished at about $80 ea...cheaper than buying new but I wasn't racing for points only open track road racing and street driving.