Two points here.
Sometimes customers prefer to have the windows shut so they can sleep. The FA's may politely request or order you to shut the window. Depends on the FA apparently and there are multiple threads about 'window' issues. So do not bank on having the window open all flight.
If you need the window I would suggest paying the $90 preferred fee. Not only will you get a desired window you will also get more leg room and should perhaps reduce claustraphobia. And given that this is likely a "HD" plane, Y will be cramped so I would advise splurging for the preferred seat.