After sending a DHCPOFFER packet to a client, how long will dhcpd wait before discarding that offer?

dhcpd holds the lease for 2 minutes after sending a DHCPOFFER.

A short lease is assigned before the offer is made and the default timeout for that initial lease is 2 minutes. If (or when) the client requests the lease, then the updated lease has a duration appropriate to the client request and the configuration options (and whether or not failover is in use).

This server-side timeout is not configurable.