I endorse the pies method!
But also, I use an Airhawk... I would say it roughly doubles the time I can spend on the bike before I need a break.
Bum ache does set in eventually though. Would love to know if there is any way of completely eliminating bum ache. I would say my arse telling me to stop is the only thing that keeps me being able to do very very high mileage days. If it wasn't for that, I'd ride all day quite happily.