I've been reading that urine that is between 15 - 20 hours old is good for killing intestinal parasites.
My understanding is this: we should not ingest ammonia, it's quite lethal. There's a tipping point when urine that is aging contains too much ammonia to be safe to drink. This (and not specifically the bacterial load) is the main reason I would be cautious with older urine and stick to as-fresh-as-possible.
The 15 - 20 hour old urine may already contain enough ammonia to kill parasites but not enough to damage YOU after one dose. But it's meant only to be taken once in a while, not every day.