Hypalon should be good for a considerable length of time. How long-well longer than you want to use/own that boat. 20 or 30 years is not a particularly long time for hypalon to last. Both my boats lasted 10 years without any meaningful leaks appearing-and when some small leaks happened it was down to my usage and general wear and tear.
The main thing to do is to pump it up and leave it at least overnight and longer if possible. Check it in the morning and see if it has deflated only a little. The boat should still be as firm as it was the night before.
If it is not as firm then the boat will need further examination to track down and patch each and every hole.
If it is leaking then it is not necessary a deal breaker. Just be aware that you are in for a "search and destroy" mission.
"Ribbing-the most expensive way of travelling third class"