restrict the adresses options that are available in mailing preferences to only show addresses that do not have an end date.
If I add a mailing preference for a constituent, I am presented with every address that is on the constituents contact tab, even if it has an end date. The only ones that do not appear are addresses that are flagged as "do not contact".
Addresses with end dates should not show in mailing preferences because we should never mail to them.
I am working with a client who has brought this up as well!