I run mine anytime I'm not on plane.

I run outboards now but I ran them all of the time in my Cigarette and Formula. I still run them all the time in our MasterCraft too.

I run em before firing up and while fueling.

This thread reminded me to buy a new Xintex fume detector with automatic blower control. My last one was so sensitive it detected an exhaust manifold leak; its ten years old and needs replacing. It can false alarm when the wind is coming from the stern at low/no speed. But easily silenced and blower will run.
Gasoline Fume Detectors | Fireboy-Xintex

Should be mandatory equipment IMO

Hate to start this debate but......

Blowers should be off while fueling!!! So should all electronic devices, bilge pump, etc. and close cabin door and all hatches. When fueling is complete hang around the dock for a bit while paying, don't be in a hurry, open engine hatch, and cabin, smell for fumes, look for gas. If all clear, then it is o.k. to run blower, bilge, etc., prior to starting.

I second that. Anytime not on plane for me. Usually end up leaving it on while running regardless....

there is some running the blower all the time info in this thread
http://www.offshoreonly.com/forums/g...rving-air.html

a visual check and sniff around, then run it for a couple minutes was all i ever did, (partially because of the jack offs at the ramp), (the guys who start the engine while backing in the water then bangin it into gear and jammin the gas and mother effin every else) theres a thread on those guys too
but a consistent by the numbers pre flight probably isn't a bad idea considering the consequences.

been meaning to remind you to post pictures of the new boat, especially those engine room hatch vents (inside and out)
bet your chomping at the bit to get that thing in the water

and when the genset is providing ice cold air in the cabin

The blowers in my boat fight against the air being sucked INTO the compartment by the engines when running since they blow air OUT of the compartment while at speed. I have noticed they get very warm and smell hot trying to fight against the flow of air. Tells me my compartment is ventilation-limited for motors. I do tend to leave them on frequently while idling or fresh off of plane to cut down on crankcase fumes from breathers.

I don't run them on plane, I don't want to suck any cool air off the bottom if there is any