One of the great yearly legislative tax games is the shenanigan surrounding the “expiring provisions” in the tax code. Congress enacts a provision in the tax code for one reason or the other but it expires after a year or two or three. In certain cases, it makes sense to have a short-lived law. However, there may be other reasons this stealth process takes place.
The most likely reason a provision is temporary is its budgetary impact. The revenue impact of a one-year tax credit, for example, is obviously much less than the 10-year impact. It is an illusion, of course. Ten year budget numbers can cause all kinds of procedural and political problems.