At what point does a high-growth company become “too expensive” to justify investing in?

I have been thinking about how investors value companies that are growing really quickly but have pretty high valuations. If a company is consistently growing revenue at, say, 30–40% annually, how much should investors actually care about its current P/E or P/S ratio? is it reasonable to accept a much higher valuation if the growth rate is strong enough, or does valuation eventually matter regardless of how fast the company is growing?

I am curious how people here balance growth, valuation, and future cash flows when deciding whether a stock is genuinely expensive versus just expensive relative to its current earnings.