Every case is unique
This is another of those how long is a piece of string questions. It is almost impossible to answer because every case in unique. Your dental implants should last you many years, but as with normal teeth, it is the quality of your home care that has the biggest impact on how long your implants will last.
If you do not look after your implants, they will develop a calculus and plaque, similar to that found on neglected natural teeth. Left untreated, as with natural teeth, this can lead to gum infection, bleeding, soreness and general discomfort. It could probably be said that implants much like teeth will last for as long as you can keep them clean.