As for the initial post:
Non-adjustable items do in fact change. One well known example is the change seen in the meter bar over a long period. Even though this secondary standard is maintained in as nearly perfect an environment as possible, it still changes. Weights, rules, pin gages, and similar that may be kept in a different environment will change faster.
If gage blocks, weights, and similar are maintained in stable environment and used only 1-2 times per year, then three years is acceptable.
Were I doing an assessment and saw a 10 year cycle, I would (and have before) write a non-conformance.
For 56flh:
Your approach is not a bad one, but depending on use I would still not go more than 2 years on the items you mention. Less if they get unduly bumped or similar.
Hope this helps.