Back to the less numeric questions, I sailed mine for over 15 years. My longest bluewater period was about 4 days and it was a pleasure. On shorter passages, I had the boat under sail in every imagineable condition from light air to 50 knots of wind gusting to 60. I survived all of it just fine. Having said that, the boat was at its finest in about 15 knots of wind with maybe 15 degrees of heel.
Two people can live aboard, but wife opted out of that lifestyle. I will agree that storage is small for that. I really consider the 31 a superb coastal cruiser, but short on storage, fuel and water for extended cruising.
I thought that PSC wnt to a completely different pedestal and rack and pinion steering on the 31 sometime after 2000. I don't know the year but I remember talking with the factory sometime in that timeframe and they were willing to send me the parts to convert(fee of course). I decided it was too big of a project. That was the only major upgrade in the post 1990 era that I remember. However, about the same time bronze hardware was no longer standard and for my 2 cents, bronze hardware is one of the great differentiators from other production boats.
Any used boat will have some trade-offs so your budget and the condition of the boat should really determine the decision.