I have been using my Citibank credit card for 12 months with a clean repayment history. How can I request a credit limit increase, and what factors does the bank consider?

I've held this card for 3 years. Quick reality check: the welcome benefit is good, the first-year fee waiver is easy, but from year 2 onwards you really have to work for the milestone benefits. Don't keep it if your monthly spend drops below the milestone threshold.