I have noticed that the chillies are not as hot now as they were just after I froze them . They were chopped whole seeds and all.
I have also noticed that dried chillies become less hot with keeping.
As a regular user of chillies/ traveller to the East, I agree that the more you eat them the more you can tollerate the heat, but I have been using them for lots of years and I am certain that the heat fades.
In fact I know people who eat them. Breakfast, lunch and dinner insist they are fresh for that reason. In fact they have so much chilli in their food, I can not taste their food for the heat.
Point of fact that if you think that you do not like 'spicy' food, build up the quantity, bit by bit and you soon find that food is tasteless without heat.