Nothing at all to be worried about in a well sorted and good running sleeve valve engine.
They wear very little and actually do tighten up (compression wise) with use. In a well sorted engine
the only noise you will hear is the carb sucking air. Plenty of power and they somewhat enjoy the higher rpm's.
Valve timing (sleeves) can drive you a little nuts but it's not rocket science.
Due to the processes and machining capabilities, each piston, inner sleeve, outer sleeve and cylinder was assigned a letter
A-D based upon it's dimensions after manufacturing. During assembly, these letters were matched with the bores .An "A" bore
will have "A" sleeves and piston. This was to achieve the tolerances sought in these engines when new.
The sleeves are cast iron and a true work of art. You never hone a sleeve but bump it round to achieve best fit.
(I didn't believe it either but it works)
A total rebuild in today's world is near impossible. Surplus sleeves and junk rings are non-existent.
Because of this, I would never attempt to rebuild another one, but I would have no problem buying a running machine.
For those that are wondering, the junk rings seal the heads (true Hemi) to the inner sleeve during compression stroke.
The heads have a small hole in the compression chamber that allows some of the compression charge to escape
behind the junk ring to seal against the inner sleeve during combustion.