Larger credit limits do help FICO, up to a point. It's like most other factors that influence a FICO score: there is an asymptote. In other words, up to $2000 CLI really help FICO. $2000 to $5000 helps FICO. $5000 to $10000 nudges it a bit. Beyond that, the effect flattens out--you've gotten all the props for higher credit limits you're ever going to get.