Not exactly sure what you are saying? Do you want the fan to stay on continuously, or do you want the fan NEVER to come on?
Seems like the fan turns on when the projector gets hot, has sensor, just like we have in home heating. It comes on when needed and turns off if goes below a certain temp. Except maybe for turn on and turn off when it goes for smooth transition.
If your home heater was always on or always off, it would be broken.
As to why PJ gets HOT! Same reason light bulbs in home get hot, ever touch one when on!
Now imagine one that puts out 2,000 lumens. The engineers who designed of PJ made sure bulb doesn't get too hot.
I was saying in my last post, make sure you put the 8200 where air flow vents around the whole unit is not blocked ( Don't putt against a wall or block sides of PJ where it forces the fan to turn on more) .
Xbox 360 had overheating problem when first made, and people would put the 360 in places where it would block fans in rear of unit, like against wall or in TV cabinet. So they were told to keep the 360 in place where good air flow could push out hot air.
p.s. As an aside to your questions about fan turning on and off properly,
I should add that the epson 8000 series might have a design flaw, nobody knows yet, because many people experience 700 hour POP on bulb. Epson switched bulb manufactures hoping this solves the problem. BUT if the unit itself can't cool down the bulb properly it would be design problem. So you can see how fan turning on and off at right time is important.
That is why I stayed away from epson for now until it's sorted out. It takes time for people to get 4,000 hours on new bulbs. And bulbs are expensive.
My post above yours had to do with BULB life, because there is nobody so far who had bulb problems with the viewsonic pro8200 that I have seen in forum or reviews.
Whereas if you look on Amazon on epson 8100 reviews and in forum rooms here, there are many threads about epson bulb problems and I saw the POLL from epson users and it doesn't look pretty.
Obviously , so far, the design of viewsonic pro8200 seems to work. And we have 3 year warranty. I mention the epson just because cooling the bulbs is very important. The reason epson users aren't more upset is because epson is replacing the bulbs free of charge, they know they have a problem. Only time will tell whether the problem is just the bulb or the unit design.