Well considering the simple fact that the op did'nt mention caliber, i assume from your lengths that you shoot a 308 or case based thereof.
Letting brass grow to the optimal trim length in your rifle can have it's advantages, if it's 2.040 the max length, at least if your not very closely measuring case growth 0.10 less is a more ideal number, you can go closer but do so on your own risk, as you need to monitor brass growth to do it safely.
Now 2.040 is really too long to let your cases stretch to as mentioned above, but trimming them down more then needed certainly has no benefit.
I let my brass grow to length, and trim / chamfer on the Giraud every firing after the desired length is reached.
But factory chambers are normally grossly oversized, so it is not always optimal, or achieveable, but certainly a dimension to keep in mind if you ever buy a custom reamer.
Trimming your brass to a consistent length every firing will help keeping neck tension and seating pressure equal and reduce SD and ES.
But if you just run them through a bushing die, and think neck tension becomes uniform as a result, while skimping on brass prep.
You have some improvement potential in your reloading process, and trimming to a consistent length is just one of the factors affecting it.
Going shorter then 2.015 as your brass comes from the factory, gives you absolutely no advantage at all, and is not sound advice.
The shorter your brass is in relation to your max chamber length, the longer time the brass will use to seal the chamber walls during firing.
Carbon deposits in your chamber, the dreaded carbon ring, is deposited by back flow, and this can be greatly reduced by shortening the gap between the case mouth and chamber end.
The slower bruning powder and the more capacity the case has the greater the benefit will be.
In a 308 with a clean burning and fast powder like the N140 this will be a lot less noticeable compared to a 7 WSM using VV N570.
With a big end clearance in your chamber, you have a lower angle(less resistance) for back flow to move into unsealed neck clearances. With this you have pressure both inside and outside the necks which affects consistent sealing, raising ES, and you see carbon sooting all the way to shoulders..
With relatively small end clearance in your chamber, any flow would be at a very high angle, and so there is less. The neck seals faster, and any small flow stops before depositing carbon at a concerning rate.
For a BR shooter or and obsessive cleaner this won't matter much, but if do high round counts between cleaning( F-class, Tactical) it will matter, and a carbon ring can be a killer during a match.
Besides getting rid of carbon rings, can require rather harsh cleaning procedures witch i am not a fan of.
If you do not believe me get a borescope and test it your self.
As i have found it also improves my ES slightly, i see no reason to not let the brass grow to optimal length as it clearly has it's advantages.
As noted though in a factory chamber this might not be achieveable in a sane manner, but going short has no advantage.
It's not basic reloading skills, but it does not mean it makes no difference.
