Not much. Did pick up a down bag and compression sack which greatly reduced volume. Also picked up the Sea to Summit collapsible bowl and cup to replace my "static" ones. They take up much less space and are easier to pack. Reduced the amount of off-bike clothes by a couple of items and picked up a pair of Xero Sole sandals that pack down pretty flat, even at size 12. I like to cook "fancy," so I have no interest things like miniature stoves and cookware. Been using the MSR Blacklite set (minus the frying pan) since I first got my own cook set back in 2000. The two pots nest, and a lot of my other cooking "supplies" (e.g., spices, can opener, cork screw, pot gripper, fit inside. I usually take one trip out west every year where the weather can be extreme, at least at altitude, so there needs to be volume for cold/wet/snow gear. (Had my 2020 trip in MT and ID not been cancelled I would have run into a blizzard.) And at 6' 2' with a broad frame, my apparel, bag and mattress are going to need more capacity than those of someone a foot shorter.
While it's nice to be able to now stow my bag in one of my panniers rather than on the outside, I have never really considered reducing volume for the sake of reducing volume. Then again, even for my first tour, which was nearly 4 months, I have never been one of those people who makes use of every cubic inch of my panniers.