I have a vague awareness that towards the end of the year it's not a good idea to put a bunch of money into a mutual fund that's in a non tax-advantaged account. Does the same hold true for putting a bunch of money into an ETF?
As a result, ETFs can and sometimes do have capital gains distributions. ... However, capital gains are much less frequent for ETF investors than for mutual fund investors, and some ETFs can go years and years without making a capital gains distribution.
OP-It depends on the ETF and mutual fund. For things that pay annually in December, that could be a problem, but many things pay quarterly, so it is not as big a deal.
One can look up the history of distributions for anything that you intend to buy and see if it matters. For most index funds, it doesn't matter if they pay quarterly and not annual distributions. For actively-managed funds, it can be a big problem.
So while you are waiting to buy to avoid a measly 0.5% distribution, the thing you want to buy could go up 2% or more. Of course, it could drop, too.