Don't see enough gain in what? Load development? Or shooting hundreds of rounds a year? I had over 2600 rounds of centerfire rifle rounds downrange in 2017. From various shooting positions out to 2000+ yards. Made my sitting position w. bipod @ 662 yard shot for my elk seem like a chip shot. Well worth it in my opinion.
I have a .308 with 18.5"bbl. I think if one is concerned about barrel life, a 110gr could meet the velocity requirement while using 'only' 50gr of powder to get there. I have mine setup as more of a brush gun, so though I typically use 180gr bullets, I can see the value of a short quick handling rifle.
It's a great little truck gun, but boy is it obnoxious to shoot. The recoil is trivial, but the muzzle blast/fireball/concussion sure isn't. If I'm expecting to shoot something in the field it's pretty much the last rifle I will reach for. I don't think I have ever fired it without hearing protection. I can't imagine what 70gr of powder in an 18" bbl would be like! Maybe it's just me, but I find 22" braked magnums more pleasant to shoot. YMMV, but either way hearing protection is your friend.
My advise would be to pick an efficient cartridge, and consider a 20" bbl, if you ever want to shoot unsuppressed that is.
Here's an interesting chart comparing overbore with bbl length.