The time horizons on each of these investments are very different.
How you invest depends on what exactly you're investing for. You might be investing money to help your 14 year old with her upcoming university tuition. You might want to invest money to live off when you retire in 30 years or so. The time horizons on each of these investments are very different. Because you'll need access to some of them sooner than others. Those with shorter horizons should invest more conservatively. Those investing money they don't need for a long time can choose riskier investments.