At age 66, the husband can apply for Contributory State Pension (COAP).
If he doesn't qualify for COAP (e.g., civil servant paying lower rate PRSI), he can remain on the widower's pension. The maximum rate of payment is the same for both pensions.
If he qualifies for a COAP rate lower than what he gets on widower's pension, he can remain on the widower's pension. The department will pay whichever is more advantageous to the customer.
All assuming the husband does not remarry or cohabit, in which case he must surrender the widower's pension.