Surely it depends on what he's describing. If it's an id that only updates once a day then he's probably right. I wrote a booking system that used 32 bit ints to reference its bookings, of which there are between 2 and 3 hundred a day. Given that anything older than 12 months old is purged even when the counter wraps round (in a couple of hundred years or so) everything will still work. I could probably used something smaller.

However if you're talking about address space then maybe when you're opening large datasets having only 32 bits will cause problems.