When is an ETF a little too high to buy?

Hi all. I have been trying to learn how to evaluate stocks and ETFs. This sub has been really helpful.

As I learned that when evaluation stocks, there are many things that you can see to judge if the stock is a little too high right now : P/E EPS or maybe even RSI in graphs.

And I have a question that, when evaluating ETFs such as SCHD, what kind of indicators would tell if the price is in a good range or too high for now? (There’s no P/E to evaluate it from)

Thank you in advance!