So, I have started submitting. I sent five queries for my SF novel tonight.
And immediately realized that in one of those five queries, I misspelled the agent's name!!!
Anyway, I will probably send a few more this week, then wait and see what happens. I have a fairly long list of agents to submit to, and the usual advice is to submit to 6-10 at a time and see how many bites you get. If you get no requests for partial or full manuscripts, your query ain't working and it's time to go back to the drawing board.