personnaly i would change my coolant each year, as a matter of course.. a bit like my central heating, new water and addative, keeps the system running sweeter than no maintainance... , and a flush out would be good to!!(every couple of years... ) as for 5 years... they have got to be kidding!!
Every year since 1986 ive drained the coolant from my cars and flushed out the rad, to stop cr4p build up, and apart from one boil over (Faulty temp sensor.. well wadda ya know!) none of my own vehicles has ever failed due to over heating...