Broadly speaking, airlines have one, and only one goal. To fill the plane completely, such that a full-fare walk-up business traveler settles into her seat just as the door closes. They have extremely sophisticated "yield management" systems to help make this happen. They will only lower prices if they think there's a danger of the plane not filling. Not for any other reason. Maybe at one time there was a Tuesday effect because of travel agents but I certainly never saw it, and it seems like most people are booking their flights while "at work" so who knows? I'm skeptical that there ever were "best times" (except for Southwest, you almost always want to book right when the flight opens). But if there were, those rules have gone completely out the window in the pandemic.
So you need to book when they think they won't fill the plane. That's hard to do, their whole job is the fill the plane. But if you can find a time when demand is dropping unexpectedly, you'll get a good fare. This can happen for a whole bunch of reasons. A competitor has added capacity to the route, leaving empty seats. Demand for travel overall decreases because people know they are putting themselves and their communities at risk, or that there's a good chance the flight will be cancelled/change routing/something else bad. Or news breaks about a particular destination (e.g., terrorism, crime, political unrest) and it's suddenly less appealing. I think your instincts are right that we're at the edge of a travel boom such as the world has never seen, so drops in demand are unlikely.
This is a very long way of saying the only thing you can do is know what a "good" price is for your route (I set alerts on
Google Flights), and snap it up when you find one you're willing to pay. There's a real floor here. It costs the airline over $300 to operate a round trip on that route, not including taxes. They're not going to be selling tickets for $150. They would cancel the flight instead (I think technically they're not supposed to but "operational reasons" can do a lot of work). But they'll certainly sell them for $600 if they think they can get it.
You can also look into "travel hacking", for coach class it's more work than I'm willing to do, but people do find deals, either by getting miles on credit cards, or last-minute sales.
