This marathon training plan has been used successfully by numerous runners aiming for a sub 3 hour marathon. My own marathon PB of 2.23 was based on this training. I adjusted paces accordingly for those aiming for a sub 3 hour marathon. For those aiming for a slower time, you can also adjust paces to work towards your time goal. This programme was initially used for an athlete I didn't know too well, who wanted general guidance. They ran a 2.56 marathon in the London Mararathon and achieved a big goal in their running career.