MRL Roller Lifter Street Durability

I am looking for honest realistic opinions on how many miles I can expect to be able
to street drive (goin' cruzin') a 400/470 with the best MRL roller lifters (with the larger
roller wheel) and a mild (approx. .580 - .600 lift) solid roller camshaft before having to
have the lifters rebuilt or replaced. What about valve spring life?

Below are the valve spring specs:

1.550" o.d. dual spring
138 lbs. @ 1.950" installed height
430 lbs. @ 1.250" open
420 lbs. per inch rate
.680" max. valve lift