Microfiche and microfilm is said to have a shelf life of up to 500 years. Unfortunately, that often hasn't been the case, as these estimates assume the film has been stored in perfect conditions, which is very rare. In the real world, film begins to break down and decay much sooner, even more so with film that is handled regularly.
So check in on your film and fiche. Do you notice any:
Bumps, bubbles, or blemishes
Has a vinegar odor
Fragility or brittleness
Stickiness
Signs of mold or fungus
Your best bet is to digitize film that shows any sign of wear and tear as soon as possible, to ensure the information is preserved before any further damage occurs.