The way I see it:
If the oa market softens a bit, who cares. Any of us can lose 10% of the value of our collections and not mind too much, especially after things have appreciated so much the last few years.
If the oa market comes crashing down, that probably means a major recession and the stock market is crashing down too. In that case, I lose nothing by having this money tied up in oa instead of crashing stocks.
The only alternative would be to put the money into cash (but inflation?), or some recession-resistant commodity (gold?), but even if I didn't collect oa, I probably wouldn't be buying gold and grain.
So, sure, spend responsibly. Only buy what you can afford. Be prepared for a possible 10% to 30% setback this next year. If things go down, as the economy recovers and stocks recover, so will oa. It's still one of a kind and people like us will still have the strong urge to buy it.
The real test for oa isn't this coming year, it will be in 20 years when many of the collectors in their 40s age out. But that's still a 20 year party and I'm here for it!