It depends on which lifts you will be skiing. The flyer, timberline express, and eagle lifts can be pretty busy, but it's not easy to predict at this point. It'll depend on snow conditions, in part. Copper has been busier this season than it has been in the last 5-7 years. Even with that, the longest I've waited in a line where the secret pass will do you any good is probably 10 minutes, and that was an anomaly. So, unless those lifts mentioned above are where you'll be skiing the vast majority of time, save your money. If you are skiing those lifts pretty much exclusively, then you might go for it : what's $40 given your short trip to Colorado and the value of the experience?