MRL Roller Lifter Street Durability

Old Man Mopar said
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

I have many engines out there that I have built, and many more around the world running our solid rollers. Most are street/strip. I have a few that are street only and have many thousands of miles on them, and we have yet to have any fail. I don't recommend rebuilding lifters, and they don't need it unless they are pushed to the ragged edge in a racing application where valve float may occur every now and again. Every time you press the axle out of the body to "rebuild" the lifter, you weaken the body.
In a street application, where the engine runs at or below 3000rpm 90% of its life, they will last just about forever, as long as the valve train is set up correctly. If you float the valves or cut off all the oil to the lifter, it wont survive no matter who's lifter you use.