Yes, you are right. I was not talking about switching to x86-64, but the fact that most code on 64 bit platforms still uses 32 bit integers and that you'll have to recompile to get 64 bit ints.

This shows up sometimes also in numerical programming, e.g. when your meshing ends up producing more than ~4.2 billion grid points. But it is quite rare, precisely because UINT32_MAX is a fairly huge number.