Hi tech-heads... A question for you.

My mechanic (who is very good and who I have a great deal of respect for), maintains that fitting a performance cam will significantly shorten the life of an engine. His explanation is that the shape of a high performance cam means the valve's transition from open to closed is far more aggressive than on a standard cam and therefore the force with which the close is greater. This greater force, he says, will ultimately and significantly shorten the life of these valves and increase the liklihood of valve breakage / issues.

Please don't pick holes in specifics I may have made one or two errors in the re-telling. In principle however, this is what he said.

Oppinions?