I've had my Biofinity monthly disposables for a month now and I love them! I can see perfectly! But they're kind of expensive, and I could save $50 if I buy a half-month supply of Frequency 55 instead of Biofinity. My dad says there probably isn't much of a difference, but I'm not convinced. The diameter would be 14.2 instead of 14.0, but I don't think that matters. Has anyone tried switching lenses to save money? Is this a bad idea?