> Btw, Constitution is a law too. Should it have an expiry date too?
Not necessarily. A constitution is a foundational law, a set of principles by which the nation is to be governed. Those principles are not expected to change very often, so no expiry date is needed. The detailed implementation of these principles, however, could - and probably should - be done with an expiry date.
Ideally, yes. But some constitutions end up being dumping grounds for laws where the amendment process was considered preferable to that of statutes (e.g. if a constitutional amendment requires approval by popular vote and therefore can't be repealed by legislators alone). The Alabama constitution is infamously over 40 times the length of the US constitution and contains 900+ amendments.
Not necessarily. A constitution is a foundational law, a set of principles by which the nation is to be governed. Those principles are not expected to change very often, so no expiry date is needed. The detailed implementation of these principles, however, could - and probably should - be done with an expiry date.