I propose a "time-based" tag, which lets people know that the question (& answer, if any) are subject to near-term exportation or staleness. The same would be applied to old questions that are dated and no longer very relevant.
Some questions are timeless.
Other questions address situations that change, such as
- demographic practices,
- uses for tools that may come & go,
- practices governed by laws that have changed.
Such a tag could also be a compromising ground against closing questions that are otherwise valuable. (this topic has come up in other SE.s)