If you buy this ETF, it would be reasonable to expect that sometime in the next 7 years, you'll see a 40 to 50% dump from wherever it has reached.

Absolutely. But if you aren't prepared to see a 50% drop in prices from time to time (not to be confused with value), then you shouldn't own any equities at all. It happens to 'em all, that's just what they do.

I don't think that the valuation of this fund is particularly attractive at the moment, since most developed world equities are pretty richly valued at the moment. I mention it primarily because I think it's a useful slate to consider, not necessarily today. Obviously a better deal if you get it at (say) 14 times earnings rather than 24.

My view is that when prices are high, best to spend your time looking for the things you'd buy when prices are cheap. When prices are cheap, spend your time buying what you've already researched and picked.

Jim