A couple of years ago I built new drawers for my stick built kitchen cabinets. I used these G-Series Knape & Vogt slides:
I also used Swingman's mounting method:
Now, I don't use the full extension feature very often, but it's nice to have when needed. What I have found is that every now and then a drawer (and it has happened to all of them) will stop about an inch less than full extension when normal pulling tension is applied. A stronger pull will open the drawer that final inch. After that, the drawer will open fully with no extra effort needed. This will last a few months and then it'll stop that 1" short of full again and require the extra effort.
It's no big deal, just a curiosity. (On the other hand, I know they will open further, but other's may not.) In any case, is it normal that these slides need to be "reset" every now and in order for them to open fully? As I mentioned, it has happened to every one of them (8) at one time or another.