Can dried peppers get hotter with aging?

You could be just that lucky to get hotter peppers recently. Chilli peppers are known to have variable hotness, even when harvested from a single plant. Most of peppers on a plant may be mild, but a few very hot.

Also, you can remember them being milder than they are if you were used to eating them more then.

I'm going to say yes. In 2013 we grew 6 varieties of mild to hot peppers. On the mild side was Poblano, and on the other was an extremely hot habanero variety. As these peppers matured we would pick them, slice them, dry them on a dehydrator then deep freeze them.

At the end of the season we had around 2.5 gallons of dried, frozen peppers. They were not stored by type but all mixed together. That Christmas we ground down the 6 pepper mix into a powder, filled several spice jars and sent them to family along with our raw honey and homemade soap. This mix packed a serious punch. I use it on just about everything and we got nothing but rave reviews from those we sent it to, all folks that love spicy food.

Now in 2015, I finally used the last of the spice so I dove into the coffin freezer, pushed aside the 2014 and 2015 harvests and pulled out the last gallon of 2013 peppers. Since they had been frozen for two years I put them on a dehydrator for 24 hours then ground them up just like I had before. I'm telling you these peppers are so much hotter than the first batch it's not even funny. This coming from a guy that can drink Siracha. If you can so much as see the small red dots on your food then you put too much on. The difference between the same peppers ground up in 2013 vs 2015 is incredible.

Chilies do not lose their flavor when they dry. What happens to a chili that dries: It shrinks in size. If you have the same amount of flavor, in a smaller area, the taste of the chili is more concentrated, and so the taste will be stronger. You can put the dried chilies in a bowl of hot water before using them. However, I would just recommend to use less of the dried chilies.
It might even be nice to use this effect, by roasting chilies in the oven, to get very rich flavored chilies.

You can get more information about this on the following site: http://www.worldofchillies.com/dried_chillies/driedchillies.html

I had a sealed glass jar of cayenne pepper that I forgot about in the back of my pantry. It wS nearly a decade old. If I use more than a pinch it’s overwhelming. It’s the same brand I always use and it absolutely was not this hot originally because I cannot tolerate overly spicy foods. This cayenne has changed over the years and is absolutely hotter. To answer your question, yes, my experience says cayenne pepper can get hotter over the years.

It's important to realize that if you use any noticeable amount of hot spice in a dish, there will be people (such as my mother) who will refuse to eat it; if you don't know anything about peoples' preferences beforehand, it's usually best to have alternatives.

I also suspect that dried chiles may have the same problem that pepper flakes have (in dishes that aren't cooked to the point where the flavors meld): unlike powdered hot spices, with flakes, you're not so much deciding how hot a dish is when you decide how many flakes to put in, as you are how many intensely hot spots there are in the dish.

Dried chiles (especially if not pre-soaked) will take longer to disperse their flavor than fresh, which would result in less overall warmth and more hot spots than fresh chilies in the same dish.

If the dried chiles started dry as in apricots, they might continue to dry further in storage, increasing that effect as they age.

Pre-soaking (regardless of whether you use the soaking water in the dish) would reduce that effect by getting the pepper ready to release its flavor into the dish from the moment it is added, giving a more uniform heat to the resulting dish.

There is a trade-off with regard to people trying to avoid hot spice with that approach: they'll be able to avoid less of the heat by trying to eat around the peppers, since more has leached out into the dish, but for people who have some threshold of hot spice that they enjoy, the hot spots are less likely to exceed it.

I have always seen peppers get less hot with age. This is from what I seen when making my own hot sauce and chili flakes from peppers I grew.

They can intensify over time for certain varieties. Others get milder. The Capsaicin undergoes some sort of unstudied transformation.