Thanks to you both for your replies. We'll be coming from Chino and the shuttle company allows 1hr50 for the trip and I would think that includes time to pick up other passengers along the way. We're visiting from Australia and will be staying with relatives at Chino before heading to Lima, connecting straight through to Cusco.

I must admit I always prefer to be early to allow for possible traffic delays etc. and since we have lounge access I don't mind additional time at the airport.