Used to have two. Went back to one. Professionally I feel like 2 monitors is a must ( excl. Laptop ). Or a single big ass monitor.
We've got ( a single ) curved screens at work. It also works because it's wide enough.
Professionally I do believe it boosts productivity. Personally/at home not really ( for me ). It can be convenient if you play an MMO and want to look something up while still seeing the game.
I do have a spare monitor but I disconnected it as I was rarely using it.