OK, I was sitting on the sideline and watching the roller vs. flat discussion "roll" on. Wasn't going to comment BUT I'm just too dumb to shut up.
First of all, I've never had an FE flat tappet solid go flat. I know it happens...but not so far to me. I've run different brands, but most of my stuff has been regrinds. One regrind in particular, I've had in 3 different motors.
I ran a 308R in a 454 incher that I picked up on Ebay. I didn't know anything about running a solid roller cam on the street, but I learned. I bought some used lifters from a local circle track racer that was running a small block Ford. They were Comp lifters, and the link bar is the difference between FE and Windsor. Changed the bars, pushrods, valve springs, and slid in the cam...and started it up.
It ran great! Picked up 3 tenths at the track. Drove fine on the street. In fact, its mannerisms were about the same as the old flat tappet. Ran it for a year and all was great.
Then one day Mrs.-T and myself were running usual Saturday errands and my car made some "unfriendly" noises and quit running. Cranking didn't sound good.
Had 'er towed home. Pulled the valve covers and there were 3 Dove rockers busted on one side, and 4 on the other. Called a racer pal and he came over with a spring checker.
You've got 90 pounds seat pressure, Tommy. That's what beat-the-crap out'a your rockers. When you loose valve control with a roller all hell breaks loose.
SO, when you say the expense of a flat tappet compared to a roller goes away if you have one go flat, that is only partially true. I've had flat tappet cams go years and years with only annual lash adjustments.
But regular maintenance with a solid roller would probably go: valve springs every winter & new roller tappets every third year.
When you add in the real world wear factor of roller tappets on the street, it gets pretty expensive.