Over the years the rates on my credit cards have changed. My credit rating improves with time and the rates on my cards go down. If the credit rating goes down, often your credit card company will raise your rates. Other cards have low introductory rates for balance transfers but then you will be paying more once the introductory period has expired. As I pay off my cards each month, the rates are not an issue for me but they still are something to keep an eye on. If you have more than one card, and don't pay off your balance in full each month, you can save some money by paying off the most on the highest rate card and trying to use the lowest rate one whenever it is possible to do so. Always look at the rates, you may see one card has raised or lowered the interest and you should adjust your usage and payments accordingly. While it is always best to pay off all balances in full, you can save yourself a lot of interest if you use the cheapest loan and pay off the highest.
I only have one card, so no, I don't regularly check its rate. They're pretty good about sending me email notifications every time something changes with my account, so I feel pretty confident that if my rate changed, they would notify me. I think by law they have to anyway, so so long as I'm paying attention to notifications, I should know if they alter anything, I think.