could you explain why the expected PV of this ill-health retirement benefit only includes past EPV ( M ia25) not future EPV(Ria25)?
It's because it's not an accruing benefit at all. The benefit is 1000 pa on retirement on ill health grounds, irrespective of the length of service. If you want to check that you've definitely got the benefit covered, try writing out Mia(25) long-hand. This should show you that all possibilities for the benefit payment are included in this one factor.
