Why is the time important when investing in ETFs?

The risk associated with each ETF depends on the asset class it invests in, naturally an ETF that invests in Stocks has a higher risk than an ETF that invests in Bonds. The higher the risk of the ETF, the longer the period of time that should be considered for the investment. If there's a considerable drop in the value of the ETF, a long-term investment allows more time to recover the value that was lost.