As he says.......... .......
It CAN be done with intelligence, it's just that most don't do that. I've done it and had engine last more than 100K. However, there are many reasons not to and disaster is waiting for you if you fit in that category.
The cam can be used if lobes are still up to height, if any is worn more than .007"-.010" you are asking for it. The high edge will be long gone by then and new lifter will not spin, rather tend to stay stay put and chew up much faster then. The lifters must still have crown on them too, they are curved on the bottom to the tune of around a 36 inch diameter radius. Much easier to get away with it with stock weak--ssed valvesprings.
Forget all that if the cam is a hi-perf one with big lobes, the high edge is gone by the first break-in of the cam and any higher spring pressures will do the cam in in as little as 30 minutes. Seen it plenty of times. I even watched some loser who 'built race engines' knock several lobes off by extreme wear simply towing manual trans car around trying to start it when he couldn't get distributor in right. Tried for 3 days to start new engine, gave up and then took it back down to find lobes missing. That was pretty wild.......... .............c am lobes lube by splash, he towed it long enough to run lobes bone dry and wear city. Why you always crank a new engine up and get it to 2500+ rpm fast so as to be flinging oil all over the place to lube the quickly wearing cam at that point. The high edge wears in pretty quick and then entire lobe begins to carry the load, by then lifter spinning is already established and it keeps on going. The wear then falls way off to begin the process of normal wear. One other reason why you change break in oil pretty quick on a new motor, to get those wear particles out of engine. And why you use break in lube on a new cam's first start up.