NT.... have you tracked the hatch rate as it relates to how long the eggs sit before you start incubation? In other words, do eggs hatch at a lower rate if they wait longer before incubation.... 14 days is a long wait to hatch. Do you keep them chilled for the 14 days? I do a rolling incubation and I have never had as high a success rate as you have. But I have big issues with too much humidity. I finally put in a digital temp controller and went a dry hatch.... but again still not at the rate of success you achieved. Congrats.
When I am storing up my eggs for a setting, they sit in my ground floor, which stays consistently 55-60F and maybe 35% RH. Once I fill a carton (12), it gets set at a 45 degree angle until I am ready to set.
For my first hatch this year, there was no discernable difference in egg age versus hatch success, but the oldest egg was only 11 days old. I saw 2 distinct days of infertile eggs, which I attribute to weather (although I did not write down actual min. temps.), but I am pretty sure those days were well below 0F, and I know I took totally frozen eggs out of the nesting boxes at that time (they become food for me).
For my 2nd setting, I had marked the egg weight on each egg when they were collected (in grams, to 2 decimal places). When I set them, I re-weighed them. I definitely notice a greater weight loss in the older eggs, but my estimate is that they were losing ~0.15% per day. My ideal weight loss during incubation is 0.67%, so the loss during storage isn't that much. My 11 day old eggs in this setting had lost at most 2.38% of original egg weight, so about as much as a 4 day incubation. I assume my first setting were roughly the same.
For my next setting, I plan on putting my stored eggs into a cooler with a small ice pack changed daily. I hope this will reduce the weight loss.