As the distributor fits into the camshaft, manufacturing tolerances might allow timing to vary slightly at the factory. All you are doing is setting the initial timing of 12º BTDC one time. The B230 series of engine with the cam driven distributor are very stable with respect to timing. Once the timing is set, it will be many years before it might be changed. Yes, it should be checked periodically, but don't expect any wear in the distributor drive to let the base timing change.
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john