I don't think it's irrelevant. Throw-away integers are really not uncommon. For-loops use them quite often, non-trivial arithmetic expressions can create a lot of intermediate temporaries. Speeding up the create-delete cycle of PyLong sounds like a very obvious thing to do.

Imagine some code that iterates over a list of integers, applies some calculation to them, and then stores them in a new list, maybe even using a list comprehension or so. If you could speed up the intermediate calculation by avoiding overhead in creating temporary PyLong objects, such code could benefit a lot.

I suspect that adding a free-list for single-digit PyLong objects (the most common case) would provide some visible benefit.