its true, old sniper t135 change to bigbore kit will lessen the life of the conrod kit.
my rough estimate is on a bigbore kit from my experience (vixion 57mm) with regular maintenance.
its safe upto 50,000kms mileage.
but what the heck!, the 50k mileage will take 2 years or more before you can
reach that
so go ahead dont worry, bore it up!
in my 5 years of owning a sniper, i only change conrod once (1.5 years ago).
and im waiting for my conrod to fail now so that i have a reason
to upgrade to faito jackup crankshaft!!! hehehe
i have a old sniper friend here,
his sniper has 100,000+kms mileage and conrod is still alive and kickin!
his stock bore reach that mileage, then we change it into bigbore.
the new 2011 sniper mx is using wider conrod bearing that it will accomodate
bigger cc boreup kits for reliability.