Time doesn't stand still, and neither does money. That's why you can use time to your advantage when investing for wealth accumulation.
The longer you invest, the more time your money has to compound interest. If your portfolio has not fully recovered from losses in recent years, you may wish to consider a more aggressive allocation to make up for lost ground and get back on track to accumulating wealth.
However, given recent lessons learned in stock market investing, it is important to remember that more conservative retirement plans typically have only a portion of the assets invested in the stock market. Other allocations should be set aside for more conservative investments and/or income contracts such as annuities. After all, the last thing you want to do is lose wealth during the next market correction.