I'm currently investing in a couple of Betterment retirement accounts, and if you have used Betterment, you know that the site makes it easy to adjust your portfolio mix of stocks and bonds (see screenshot below of the eye-catching website GUI).
My instinct is to allocate a larger portion of my portfolio in stocks during a bull market (such as the one in which we now find ourselves), but then dial that back to a larger portion of bonds during a bear market. For example, this strategy might lead me to ride the current stock market wave at 80/20 stocks to bonds, but if/as the stock market starts slowing or falling, drop to 50/50 stocks to bonds (or even a lower stocks percentage).
Tax implications included, is this a good long-term strategy? I'm 30 and wondering if this will pay off over the coming decades until I retire, or if this strategy will just rack up larger tax bills for myself and require that I watch the market like a hawk, fingers twitching at the dial.
Thanks for the help.