"Any" kind of lapping reduces barrel life because it removes barrel material.
It may be necessary to condition a barre to shoot better for the short/immediate time to this has to be considered before embarking
on this process.
A premium barrel should not need to be lapped because most are lapped by the barrel maker before it is sent out. factory barrels are not
because of cost and some need it and some just need time and shots to get better.
Lapping a barrel can be a delicate process that only removes the necessary areas that are bad. also special care should be used when lapping a finished barrel to prevent the muzzle or throat from being enlarged during the process. Just like reversing a bore brush without clearing the muzzle or the throat can do damage to those areas. doing the same thing while lapping can do the same.
Normally, when a custom barrel is lapped, the barrel maker solves this by forcing you to cut of the first 3/4" of the muzzle. the chamber end does not need this because that end of the barrel bore will be removed by chambering.
Fire lapping only addresses the throat end and buy the time the abrasive projectiles reach the muzzle most if not all of the abrasives
are spent and no longer do much for the bore.
I have done lots of both types of lapping and always look for the results with a bore scope . Lapping done "correctly" does the best job in my opinion of uniform results. fire lapping is faster and a lot less trouble (Also if done right). but is less uniform for the entire barrel bore.
If a person buys a factory rifle and the bore is rough ether system will improve it for the short term. If It is a hunting rifle that may not get more that a box of cartridges through it a year, It cant hurt.
The main advice I can give is to do ether sparingly and no more than need to be done to reach some desired accuracy standard.
J E CUSTOM