IF you let them make a few dollars in interest by not paying off the entire balance they will drastically raise your credit limit. you know why.
It is fairly rare when I get an automatic credit card increase. I have a couple of rewards card with a money center bank. They pester me every time I login for my income, which I decline to give them. I have a CC with my CU. They have an idea of my spending and bill paying habits and never ask me for my income when I login.