Most cost effective tweek is probably getting your speaker placement correct. Depending on the speakers an 1/8” move in the right way can have a significant impact.
As far as break-in. I do my upgrades over a short time (say a year)… typically many components. Then I don’t upgrade for 5 to 10 years.
Break-in is a big problem during the upgrade cycle. Particularly with tubes… solid state I will run 24 by 7 for several weeks. I have a cheap system to break in power cords and interconnects. For most of my components the stated break-in is 600 hours. But the big changes happen in the first 200 or so. A number of people have remarked that it goes beyond that. Most of my current components ended up being very close to the same number of hours (my audio guy brings over a demo unit, and if I like it, I keep that until delivery of my own unit). I noticed slow improvement over the 600 to 1000 hour range. A nice treat for the post upgrade cycle.
As far as break-in. I do my upgrades over a short time (say a year)… typically many components. Then I don’t upgrade for 5 to 10 years.
Break-in is a big problem during the upgrade cycle. Particularly with tubes… solid state I will run 24 by 7 for several weeks. I have a cheap system to break in power cords and interconnects. For most of my components the stated break-in is 600 hours. But the big changes happen in the first 200 or so. A number of people have remarked that it goes beyond that. Most of my current components ended up being very close to the same number of hours (my audio guy brings over a demo unit, and if I like it, I keep that until delivery of my own unit). I noticed slow improvement over the 600 to 1000 hour range. A nice treat for the post upgrade cycle.