The "actual" chamber lengths are usually about .020 over the Max trim length.
My BR brass lists a Max trim length of 1.560 and the "Actual Measured" length of the chambers are 1.584 to 1.585 so I know I have a long way over Max before I need to start thinking about trimming.
And it depends a lot on the type of resizing dies you use. Full length dies with the expander ball will pull the neck longer compared to shoulder bump/bushing dies.
On 99.99% of all my brass, I use shoulder bump bushing dies and my brass doesn't grow. Bushings size the neck, shoulders get bumped back maybe .001 to .0015 and size with a body die if the case starts getting snug in the chamber.
(maybe every 5th. or 6th. firing?) No trimming needed or very seldom. 8)