For the purpose of discussion, lets say you're using J & B Imports for your motor work. Call Bud at (714) 282-7378 or e-mail to jandbimports@abac.com and tell him that you're sending over a crank/piston assembly. Ask him to rebuild the crank and replace the pistons with the next oversize (usually 1/2 to 1 millimeter over). Bud will probably ask if there are any deep scratches in the bores that might require an unusual amount of boring to smooth out. If Bud needs the diameter of the bores or old pistons, no problem; your local engine rebuilding machine shop can measure them for you.
Oil Change
The best way to increase the longevity of the balance shaft gear is by keeping the fan belt adjusted as loosely as possible while still avoiding belt squeal. This will prevent undue strain on the balance shaft bearings. Of course, regular and frequent oil changes will extend the life of all the bearings in the engine. It should be noted that in the USA, "factory" air conditioning was installed at the dealer. Part of the factory-recommended installation procedure was to replace the fiber gear with a steel version. It has been found that this part of the procedure was often ignored by dealer mechanics, leading to an exceedingly short balance shaft gear lifespan due to the inordinate stress the A/C compressor places on the gear when in operation. However, if you come across a car with air conditioning installed, the steel gear may be in there -- a big selling point.