spark plug coils

I was needing to know about how many miles are the spark plug coils good for? Thanks.

A lot comes about these on several forums - mine are still OK - and mileage was not a direct factor but very often oil leakage from valve cover gasket was . ALso mishandling when taken off for spark plug change. I also suspect extreme heat specially when reported by modified off-roaders/mountain climbers and the like.
I recommend you consult
THIS (www.4x4wire.com/forums/showflat.php?Cat=&Number=653021&page=0&view=collapsed&sb=5&o=2&fpart=1)
if you attempt to change plugs or play around this area.

Thanks LMP. I'm at 85000 miles now and will probably change the plugs and wires around 90000. I will have to inspect the coils when i get in there.
sport01