Well there's no time like the present. If it was me I'd set up a price alert on Google Flights (numerous videos out there on how to do this) and give it a few weeks to see what comes up. Generally "good" NYC <> continental Europe prices in business class hover around the $2000 - $2500 range round trip. often via cheaper gateways like Lisbon rather than nonstop, but there are exceptions. You might want also to monitor prices ex-Montreal or Toronto as sometimes there can be significant-enough differences to offset the "staging" cost to get up to Canada.

I also recommend monitoring this board on Flyertalk - Premium Fare Deals - FlyerTalk Forums - where the wonks spot good fares more quickly than most. You might see some fare from/to some other cities than NYC or Madrid, but again, the savings might be worth the extra logistical challenges. Good luck!

Great reply Gardyloo.

>> when should I begin looking?
For March 2024 you sh/could begin looking anytime from April 2023 to now. :)

>> $2000 - $2500 range round trip. often via cheaper gateways like Lisbon rather than nonstop
That is the price range I had in mind for a good fare. I might buy it if my dates were not flexible. I would consider that to be a very good price range for nonstops and would buy it immediately.

Here is a GF search with five origin and two destination airports:
You can use the Date Grid to find your date. Sure enough, there is $2505 via LIS on TAP. The Azores Airlines fares look too good to be true for intercontinental business class, but maybe it is something like a nice premium economy.

Here is an ITA search with a flexbile trip duration of 10-14 days. You can click on Modifty Search to make changes, like selecting Nonstop only or to add/remove airports.