In California a bike lane is probably good forever once its laid. There are vehicular roads in my neighborhood that are from the 1920s. These are roads that see construction vehicles and cement trucks abusing them for the past 100 years to infill more housing into the neighborhood, along with your standard semitruck based home movers, delivery vehicles, garbage trucks, fire, etc, and still work fine for roads.

A bike lane on the other hand deals with at most probably a 300lb vehicle. Bike lanes in CA especially would probably last as long as the Appian way if not longer.