[inyourtenement]

Don't time the market. Timing the market gives you two chances to screw up -- when you decide not to invest, and then when you decide the time is right.

Or to put it more concretely, there is a long chain of "all-time highs" before the last all-time high. You would miss out on all that investment time if you avoided the market based on all-time highs. And then a correction comes -- but is it the one you were expecting or is there a bigger correction in the wings?

In the end, one never knows. None of the rules of thumb are reliable. And you can shoot yourself in the foot far more by trying to time, than by just buying and holding.

[meric]

You're timing the market if, for whatever reason, you haven't invested in the past 5 years, and now that the market is at all time highs, decide to allocate 100% of your assets into the market.

I hold my suggestion to the OP, keep a portion in cash.

[inyourtenement]

That's not really true, and not what people mean by "timing the market." Thinking the market generally goes up and one should invest in it is not timing, no matter when you think it. Repeating the phrase "all time high" as though it indicated the future is precisely timing.

It's been shown that if you have a lump sum of money, it's most often better to dump it all in the market as soon as possible, rather than gradually buying in.

Of course you shouldn't put 100% of your money in the stock market, your advice was reasonable.

[meric]

I still think, unless you're investing a constant amount of money every X period, you're timing the market, since you're still subconsciously or consciously picking when to invest into the market depending on time.

The pitfall with "Thinking the market generally goes up and one should invest in it is not timing" is, the thought only occurs after the market has gone way up, rather than occurring unbiasedly between instances when the market has gone way down or way up.