How long is a season?

I would spray as needed. I am never bothered much by bugs - I don't leave anything edible for a mouse in the blind ever.
Snakes are not a problem for me but I surely would check if i was in slither headquarters.
One thing to consider leaving a blind out. Those Avery blinds or any any blind using that Nylon type camo material may fade or turn blue due to the ultra violet rays.
Be aware of that.
My DBs don't - because it is a canvas type of fabric.

JW