Everyone over reacts, including sponsors. The media made this a lot worse than it was imo. I support the sponsors decision to cancel the contract but when you look at what others athletes have done, this is as much of a non-story as you can get. If he told his mother the truth I doubt we'd even know it happened.
Cast irons are pretty tough and it's unlikely the extra range time would do much damage to them compared to what happens to clubs on the course. I would practice with the clubs you play with and now worry about the extra wear and tear.
I don't, and I don't think it would ever be a good idea for me. My swing is inconsistent enough without spending my range time hitting clubs with different head weights, swing weights and distances, then show up at dawn for tee time and have to readjust in about 15 minutes to my game sticks.
Besides, my current irons are G10s; cast, almost 10 years old and bought used, so there's not a lot of motivation for me to try to save them by hitting anything older or more beat up. And when I get new irons, I'm going to be looking for a set with a little less forgiveness (Ping i-series, Mizuno JPX Pro etc) to force myself to dial in my ball striking, so the newer set will actually be my range set until I feel good enough with them to game them.