It sounds like he has some real issues regarding money and health from his parents. 65 is still very young these days, compared to the past, and most people will still be very active into 70s and 80s, my mum was. Some do die young still, a colleague died a few months ago of complications after a heart attack, he was 60 and a few months, so no retirement, but that has made me realise I wont work longer than I have to.
BUT - there has to be a balance, you have to live for today too.
Can you talk to him, come to some compromise regarding his inheritance, or are his problems too deep? Would counselling maybe help him to see he should have a balance?
As I said in my earlier post, we came into money last year, from my mum dying and from a share sell off at my work. My colleague also got the share windfall, but didnt live long enough to enjoy it.
So although a lot of our gain is going into our ISAs, we are also doing things we want to do now - upgrading cars, going to USA in summer, whilst DC (17 & 19) still want to come. Not scrimping on the trip, making sure we have a holiday to remember. We are also generous with DC, helping with uni costs etc. Always up for taking DS out when we visit, or for a supermarket shop. Little things which help him, but which I am guessing your DH would not want to spend money on.
We also like walking, cycling etc, but think nothing of stopping for a nice meal on the way home, having a lunch out if on a bike ride etc. Life is for living, you are a long time dead and you cant take the money with you.