I've been with Discover since 2014 (when just entering college). I never missed a payment with them, however, I did have my spending suspended for about 4-6 months when I ran into some trouble and took a credit hit that I am still recovering from...
I got my spending privileges back about 4 months ago and last month I switched from the IT Chrome to the IT (5% rotating category one).
Just today I entered in my new employment info and income and pushed the submit button... instant doubling of my CL. So I went from $500 to $1000 today (since 2014). Not my biggest credit line, however, this gave me some hope on my seemingly forever credit recovery! 
Congratulations on the increase!