The use of hevishot is as bad for your barrel as is steel. The problem is that the steel/hevishot does not compress as did lead, therefore there is a possibility of the barrel bulging as the shot column is initially moved forward. This is also the concern with a tight choke.
But now we have a new option (once again expensive) and that is Hevishot Classic Double. It was designed and marketed towards the "old expensive double barrel" guns. As I read their advertisement it says "26% denser than steel, but soft like lead. We would need to buy pre-loaded shells and take them apart.
http://www.hevishot.com/products_doubles.html
I still have some bismuth left in #2's and #5's, but next season I'm going to consider the new Doubles Classic.