Not everything expires at the same rate
An emergency lead from three weeks ago is gone — the pipe was fixed by someone that night. A quote request for a roof replacement or a recurring cleaning may well be open, because those decisions take weeks and often stall.
Sort your unanswered pile by job type before deciding it is worthless. Urgency is what expires, not interest.
Do not pretend it did not happen
Reaching out three weeks later as if nothing happened invites the obvious question. Acknowledging it plainly — that their request came in during a busy stretch and you are following up now — costs nothing and reads as honest.
Then fix the reason it happened
Recovery is worth doing once. It is not a system. If leads went unanswered because everyone was on a job, that will happen again next week, and the recovery pile will refill at the same rate.
The number worth knowing is not how many you can recover, but how many you are structurally unable to answer in time — that is the one that repeats.