Labs take a lot of time, yes. But if you work hard your supervisor will give you a fantastic mark that will pull your marks up. Unlike other courses where effort can be wasted on poor test marks, a supervisor will reward you effort with a good one.
It's a drag working 30 hours a week in a lab (when the 'reccommendation is 8), but you'll get the benefits...that is unless you're a complete ass who does nothing.
good luck