Last time I went through a major BAA airport, the M25 had taken a 90-minute chunk out of my hour's contingency so we arrived in the terminal building with two and a half hours to go. Queues at check-in (we got hauled out of the queue as our flight got ever-closer to departure and put through a priority one with no wait), more queues at security and we ended up whizzing through the entire shopping experience to get to our gate on time. We weren't late, but we missed the entire BAA money extravaganza. What a shame. The only money we gave them was for some bottles of water from the vending machine by the gate. Oh, and I discovered a container of lip balm in my coat pocket that never got declared at security. Fortunately it behaved exactly like lip balm for the entire flight.
If they want us to spend more time shopping then either fix the M25 or the terminal queues.