While identification of key risk factors for mortality has contributed to advances in healthcare, the effect of these risk factors in predicting mortality over different time horizons remains unclear. We sought to determine how risk factors predicted shorter-term and longer-term mortality across the age spectrum in adults. We used data from 11 247 adults of the Australian Diabetes, Obesity and Lifestyle (AusDiab) study. Cox multivariable regression models were used to estimate hazard ratios (HRs) of shorter-term (0-10 years) and longer-term (10-20 years) all-cause and cardiovascular disease (CVD)-related mortality associated with risk factors. Models with interaction between baseline age and each risk factor were also fitted. During a 20-year follow-up, 2185 deaths occurred. Smoking, diabetes, male sex and albuminuria all independently predicted shorter- and longer-term all-cause and CVD mortality. Most associations were stronger in the shorter term compared to the longer term. A notable exception was the association between smoking and CVD mortality, which was stronger in the longer term (HR 3.55, 95% confidence interval (CI) 2.57-4.90) compared to the shorter term (HR 2.06, 95% CI 1.33-3.20). The magnitude of association between most risk factors and mortality attenuated with age. Classical risk factors for total and CVD mortality remain important up to 20 years after their measurement. In unselected adult cohorts, longer-term follow-up (e.g. beyond 10 years) may not provide additional information on associations of risk factors with mortality beyond that obtained in shorter-term follow-up.