The most important thing for the longevity of an implant after its placement procedure is the health of the gum around it. Good oral hygiene and cleaning the teeth and gums, specially around the implant, is very important.
Smoking is harmful for the gums and will shorten the life of the implant. Some medications, medical conditions and those who are genetically predisposed to periodontal disease (gum disease) are amongst the people who may lose the implant sooner than expected.