I did this for a while, but then at some point Barclays decided that since I wasn't utilizing a decent portion of my credit regularly, they needed to reduce my limit by 2/3rds. When I called them they said it was to protect me, so that I wouldn't accidentally spend way more than I regularly intended. Even after pointing out that my income didn't reduce, so my ability to pay the already approved credit limit didn't reduce either, I would still have to apply (with a hard credit pull) to get the limit reinstated.

And of course, a reduction in credit availability tanks your credit score for a bit, so I doubt that I would get approved for the limit I already had. I don't even think it was that large of an amount, something like 10k before the reduction.