I have followed several threads here about pistons and liners being removed for cleaning or other tasks.

Back in the day...I was always told to not disturb the piston/liner assembly because the microscopic grooves would never line up and the engine would require another break-in, subsequently wearing parts in a different spot, reducing the life of the engine.

Are today's liners and pistons that much better or have some of the old rules just gone by the wayside?

I have followed several threads here about pistons and liners being removed for cleaning or other tasks.

Back in the day...I was always told to not disturb the piston/liner assembly because the microscopic grooves would never line up and the engine would require another break-in, subsequently wearing parts in a different spot, reducing the life of the engine.

Are today's liners and pistons that much better or have some of the old rules just gone by the wayside?

Most of the recommendations not to disturb a sleeve come from the Fox engines.  Most of the early ones, prior to the Schneurle ones, used very thin sleeves and a fairly small lip on the sleeve.  Plus they tended to be, shall we say, less than perfect in the machining of the sleeve, so the lip might be slightly cocked.  Once the engine was broken in it could be impossible to get it back together exactly as it was.  The trick was to spend an hour or so tweaking the headbolts down without introducing a bind in the sleeve.  You have to clean the piston and sleeve very clean so there is no oil on them.  Install the piston, sleeve and head.  As the head bolts are tightened, going back and forth every other screw.  After every little twist turn the engine over and make sure there is no bind.  If one appears back  off the last screw tightened a tiny bit until the bind goes away and then continue.

Most of the modern engines with ABC construction can be disassembled and reassembled with little trouble, as long as everything is spotlessly clean.  Tiny bits of dirt under the edge of the sleeve or head can cause trouble.  Some of the engines made in China have fairly poor tolerances and can be as troublesome as the old Fox engines.