Snap and Pinterest posted stellar revenue growth for the third quarter, sending their stocks to record highs and putting their valuations well above those of social media peers Facebook and Twitter. Whether they can maintain those valuations, however, depends on whether their recent advertising gains are sustained.

Media buyers and advertisers say Snap and Pinterest should be able to pull that off. The bottom line: They’ll need to make good on the investor assumption that the pandemic has been an inflection point for their businesses, accelerating their growth.