A fixed ratio like rebalancing? That’s not really timing the market as you typically rebalance after a set period regardless of how the market has moved.

But you still money money the opposite of how the market moved.

Rebalancing is really taking money out of whatever the better investment was and putting it into what was the worse investment. Consider what would happen if you rebalance an asset like a stock that’s slowly going to 0. Over time your portfolio also hits ~zero even if everything else was going well.

Sure, for a sufficiently diversified investment like the S&P 500 it’s unlikely to hit zero. But the question stands why take money out of the better investment for 50+ years? You could be moving from 10% returns to 2% returns. The theory is about timing the market, you get better returns investing after ups than downs.

PS: Though better may in fact relate to stability more than absolute percentages.

Timing the market is exactly what you said about saving cash. Changing your asset allocations based on age or other milestones is not timing the market in any way. It’s reducing risk if you are about to retire.

Changing your asset allocation yearly or quarterly based on news is foolish. I’d call that timing too.

As I said a fixed asset ratio is timing the market. The expected returns for socks are higher than bonds, it’s rebalancing that makes fixed ratios a good idea.

As to changing asset ratios, it likely reduces maximum returns. But, wealth has diminishing marginal utility. I can save a little more to make up for a small loss in returns for a few years, it’s much harder to make up for a 50% market dip.