The pros have different monitor speakers and also know their baseline speakers like the back of their hand. The reason they're called
professionals is because they have developed and ear for what will work in the majority of listening environments and what won't.
I've been mixing for a long time but I don't do this 12 hours a day. So I too listen to my mix on headphones, monitors, in my car, with earbuds, etc and make adjustments along the way.
I do use
TB-Isone which simulates different environments and speakers but it's only an approximation and just speeds things up a little bit. But it's pretty good for the price.
Like the saying goes, a mix is never finished, it's abandoned!