The textbook definition of a recession may mean that prices will continue to fall until the recession ends -- in fact, as soon as prices rise it ends the recession. But by that definition, the "great recession" ended in the USA in June 2009.

I'm guessing the above poster meant something more like "period of society-wide economic hardship" by recession. By that more colloquial definition, you might say the great recession lasted through 2014. The stock price plummet, however, was largely finished for most of that period of hardship.

I have no crystal ball; I can't tell you where we are going to be. But if the above poster meant "We're past the plummet, all that's left is the slow climb back to normalcy" then their comment makes more sense.

First, there is always the possibility that I could be wrong. The markets could hover around these levels and fall no further. Second, I may not know when to buy back in. Do I back in after they have fallen 10%? How about 20%? Should I wait till 25%? What if it goes down another 3% and then starts to head backup.. and then back down again above these levels before falling another 30%?

What you are suggesting is market timing. I am not very good at it, and I don't think most people are. You not only have to know when to sell, but you have to know when to buy back in. You have to get it right twice.

Perhaps. A 30% spy drop is already in predicting recession territory (https://www.investopedia.com/a-history-of-bear-markets-45826...). Even if I was 100% confident there would be a recession, it's still not clear the markets are not undervalued at this point.