Most operators quote an average speed to lead and feel fine about it. The average is dominated by the leads that came in at 10am on a Tuesday while someone was sitting at a desk. It tells you nothing about the 8pm lead, which is the one you lost.
Export leads created and first outbound attempt for the last ninety days. Bucket by hour of creation. Look at the median response time in each bucket. The shape of that chart is the actual story, and for most shops it falls off a cliff after 6pm and never recovers until morning.
Under five minutes, in every bucket, including 2am. Not because 2am leads are common, but because the leads that arrive when nobody is watching are the ones your competitors also aren't answering.