My target AA was 55/45 for most of my working years. The stock side rose during the late 1990s boom years. I did some minor rebalancing in 2001-2002 when the markets tanked, and in early 2003 when the bond fund prices spiked.
But there was one area where I sometimes regretted being too conservative.
The company stock in my retirement portfolio (basically "found" money) exploded in value from 2002-2007. However, once we were allowed to divest a portion of it (the company had not yet gone public, so we had to hold most of the shares if we remained employed), I chose to do that. This was in the wake of Enron and other company failures which wiped out company-stock-heavy portfolios, so I was a little jittery about having so much money tied up with my company stock.
When I was doing this divesting, I hadn't yet put together my ER plan which included a magic number for the stock value. Once I created a magic number, I stopped divesting any more of the company stock.
But there was an upside to delaying my reaching the magic number for the company stock. By late 2008, when I finally reached it, the markets had been tanking for much of the year. The big bond fund's NAV tumbled, so I was able to buy ~25% more shares than I expected. So, I had less money from the cashed-out stock but bought cheaper shares with it.
The proceeds from the divested shares now reside in my rollover IRA, growing tax-deferred for now. And the tax bite on the cashed-out stock, despite using NUA, was still about 25%. So, it is hard to tell if I would have come out ahead, behind, or about even had I not done the divesting and retired 6-12 months earlier.
In any event, I don't regret how things turned out.