Drip feeding versus going all in

Should you invest a windfall all at once, or spread it out over a year? The honest answer is uncomfortable: going all in usually makes more money, and spreading it out usually helps you sleep. Both facts are true, and pretending otherwise is how bad advice gets given.

What the evidence says

Markets rise more often than they fall. That is the whole argument. If the expected return is positive, then time out of the market has an expected cost, and money held back to invest later is money not compounding now. Across historical data, lump-sum investing beats drip feeding roughly two thirds of the time.

Press "new market path" a few times. Lump sum wins most of them. It loses badly on the paths where the market falls immediately after you commit, and those are exactly the paths that terrify people.

What you are actually buying

Averaging in is not an investment strategy. It is an insurance policy against regret, and like all insurance, it has a premium.

The premium is expected return. What you get for it is a smaller worst case, and, more importantly, a much higher chance that you actually go through with it. An optimal strategy you abandon in month two is worth less than a suboptimal one you follow for thirty years.

The case that is genuinely different

Investing your salary monthly is not dollar cost averaging in this sense, and the comparison does not apply. You are not choosing to hold cash back: the money did not exist yet. You are simply investing as you earn, which is optimal by default. Do not let the debate confuse you into hesitating.