Credit card companies typically allow you to request a credit limit increase once or twice per year, per account. Getting higher credit limits by requesting increases with regularity will enable you to take advantage of your good payment history and potentially result in a higher credit score.
About 30% of your credit score has to do with the amounts you owe your lenders, which the credit bureaus "score" by looking at your balances as a percentage of your available credit limits. This is referred to as "credit utilization," or the percentage of your credit limits you use on a regular basis.
For example, someone who has a $1,500 balance on a credit card with a credit limit of $5,000 would have a credit utilization ratio of 30%. ($1,500 balance ÷ $5,000 limit = 0.3, or 30%). As a rule of thumb, a lower credit utilization ratio lends itself to a higher credit score, all else equal.
Source: Fool.com