That is pretty good claimed hp numbers. I pull a camper, and I could use the torque. How much are we reducing the life expectancy of the engine?
This is really a "he said she said" topic lol. IMO you don't reduce life at all. That said, if you drive it like it's a formula one race car because it's tuned, then yes it's not going to last as long. But if you did that stock then it wouldn't either. So it really makes no difference, all it does basically is add timing advance and maybe changes fueling slightly. I've several friends that have had 3rd gen hemi rams that ran over 100,000 miles with their SC's (always tuned with 91 tune) and they would race them at the track often, and when they sold the trucks they had no problems. My friend's camaro has like 160,000 miles he's had the diablo and SC for over 100,000 miles and races his car a lot and has had few problems (none really related to tuning.....he had a rear differential issue, a cracked flywheel, and bad rear main seal leak...none caused by tuning).
Just make sure you use the correct octane for the tune and you will cause no damage.
One thing to make note of: The SC gives you control of torque management, and if you disable or reduce torque management you can possibly shorten the life of your transmission. Now like I said my friend's have had no issues with their 3rd gen's, but my point is that if with factory tuning the trans would last 1,000,000 miles, maybe with the TM disabled it would last 500,000 miles. So it may not matte to you, but just something to be aware of. You don't HAVE to mess with the TM, just an option.