[dageshi]

For a retirement portfolio I'd likely stop buying and save cash for a correction and start buying after a significant decline/crash.

In doing so you lower your average buying price and have cash on hand if you need it.

[refurb]

Problem with that approach is when the market does recover those gains can come quickly. Missing out on just a few days can cut your returns in half.

Better to stay in the market and keep rebalancing your portfolio. That way your 100% invested at the bottom.