I know there are guys like Brandon Sanderson who can write the wheel of time and Mistborn at the same time and have them out within a year or something, but I can’t imagine that's common, even among experienced writers.
Not everyone can multi-task (boy, I wish I could!), but the majority of SF/F writers, even of doorstops, put out one book a year on a series (though they might take time off between series). The GRRMs, Lynches, etc, are exceptions, not rules. It's not a good idea to bank on anything in publishing, and especially not on being an exception.
And heck, I'm pretty sure GRRM
is putting out at least one book a year, just not ASOIF.
I understand dreaming and reaching for stars. We all have to do that.
But you're in a forum asking for factual answers, and that's what you're going to get. The fact is that most publishers do expect a book a year. Doesn't mean they all do, doesn't mean you can't get a contract with longer time between. It might well happen. But if you're asking about what's typical, well, there you go.