I have a flat tappet camshaft running composite Smith Machine custom made lifters in my Ford windsor engine, spring pressure is below 440Ibs open.
I would be a bit disappointed if this engine only made 8000 miles on this camshaft as most of the mileage will be cruising at highway speed, with good lubrication
oil high in
zinc etc.
I guess it depends on how hard the race miles are as my engine might only do 2 - 3000 miles per year so it would take 5 years to do and then it may be prudent to strip it and do the valves springs etc. Running the 100 rockwell hard ceramic puck type lifter maybe a bit risky if you get too much valve clearance the bonuses of this lifter are less risky camshaft run in and less friction.
Time will tell......!