By increase the risk level to get 10% return, it would take 4.08 years (48 months) with $3000 contribution per month.
With dividend reinvestment, you are buying more shares with the dividend you’re paid, rather than taking the cash. The biggest advantage of reinvesting dividends is the power of compounding returns over time. Your dividends buy more shares, which increases your dividend the next time, which lets you buy even more shares, and so on. In a lot of circumstances, reinvesting the dividends can super-charge your returns, and that should be your first choice if you want your dividends grow faster.
Here is some of the math to prove it:
Say you invest $10,000 in Enbridge (ENB). On Jan 4, 2000, the price of Enbridge is $4.91, this will buy you total of 2037 shares. By reinvesting these dividends over the span of 20 years, on Jan 4, 2020, the number of share you are owning with our original $10,000 of investing is 4416 shares. On Jan 4, 2020, Enbridge was paying $2.30 in dividend/share at the price of 39.71. You would be collecting $10,159 per year in dividends and your original investment would grow to $175,399. Your total return is 1654% or 15.39% annually.
But if you say no to reinvesting dividends, your total return on $10,000 invested in Enbridge 20 years ago is 1073% or 13.09 annually. The end investment is $117,238 and the difference is $58,161.