For anyone that has the same question.
A workaround I've found is the Arpwatch package. It has a Timestamp data that has the last seen time not only for DHPC clients, but also for hosts with static IPs which is amazing!
It does the job perfectly but has the following cons:
there is no convenient way to remove specific entries from the Arpwatch database;
in order to find the last seen time of specific host from the DHCP lease table, I have to manually crosscheck the info from both services;
sorting the database of Arpwatch is done by the letters of the days of the week, not by the date itself which is quite unusual and a bit silly.
Regards!