To give you an idea how tough this nicasil is, here are the replacment mileages for my Honda RS race motor. Piston ring 125 miles, piston 250 miles, crankshaft 500 miles and last of all the cylinder 1,000 miles, it's real tough stuff.
In a big four stroke motor, it'll probably out live you.
As a rule, it isn't overbored, it's replated, but it can be removed, overbored and replated to acomodate a larger piston as in my race motor. (125 is now 134cc +2mm)
Sam.