Bicycle shorts fit: do leg grippers stretch out?
The short answer is "sometimes". There are a few different styles of leg grippers.  Some are more likely to stretch than others.

Thick Silicone leg grippers, in my experience stretch the least and are the least comfortable. While they do a great job of not letting the pant leg slip, I find the level of discomfort not worth it.


My favorite kind have a slightly different material than the rest of the short, similar "strechiness" but only slightly tacky on the inside. These, I've found do stretch out over time but in similar fashion to the rest of the short's material.


There are some shorts that have the tackiness of the above type but bind a little more and can stretch over time.  I have a few pairs but the wider the band the more tolerant I am of the binding


There is another type that tends to stretch out which is, more or less, a cinched, folder over piece of the same material found in the rest of the short. As mentioned, they do tend to stretch out and don't often stay in place as well as the tacky kinds.
There are also grippers that have little silicone "dots" to help hold in place. I usually find that they're less binding but they can be put on any material so the stretch durability is hard to nail down