Well when it comes to retirement in football it something that has to do with person interest, imagine being in the system for over 15years, barely having time for your family, friends, kids and not being able to do some stuffs, all these are thing that trigger retirement in football. There are some who would even retire at their late 20s. So I would say it all individual differences when it comes to retirement in football.
Some do retire on health grounds too not just that they have not had time and chance for their family and themselves, there are players who suffer series of injuries at a stretch and they will just end up not wanting to continue playing because they have been advised medically or they see themselves been at serious risk of having some future health challenges which they can avert by retiring and changing their kind of profession and for some.they get life threatening injuries and they are left with no option but to retire so they can have their lives back.