C'mon, kids, play nice or they'll take your crayons away!
Seriously, though, I have both rollers and flat tappet engines with 300K miles on the same cam. Then, too, I've had both fail in less time, some went south in no time at all. The critical time with flat tappets is the first minute or so after initial startup. If it fires right up with no problem and runs easily, and there's a good cam lube and zinc additive used, I have had no trouble at all with modern oils. Not to say rollers aren't better, just not absolutely necessary for a street engine.
As for heads on a 460, the C3's can be made to work well if you are rebuilding the engine anyway, just buy the pistons needed to put the CR where you want it and port the heads a bit to get rid of the restriction in the exhaust ports. And of course get a timing set that is straight up, not retarded like the factory ones.
It's not just the retarded timing sets that kill a stocker, the cams have a profile reminiscent of a Stovebolt Chevy 6.