I've never had a horse I owned die under any circumstances - yet!
I think I would prefer (if that's the right word) my horse to be of a certain age (ie. over 10) and die doing something he/she loves than breaking down on the gallops or suffering a horrendous fall on the track and having to be shot!
No one likes losing a racehorse under any circumstances, but if I had a 12 yo horse and he/she loved racing, I wouldn't stand in his/her way - in fact I would positively support the trainer. If the horse died of a heart attack on the track, although I would clearly be heartbroken, I certainly wouldn't be looking to blame anyone for the loss. I must admit I would be thrilled if any horse of mine was still wanting to race at that age.
It's slightly different with Bay Hawk, as he has a ticking time bomb in shape of a tendon injury - that although is fine now, could cause him problems in the future. He is a racehorse, he loves his racing and I trust Brendan and his staff 100% to keep an eye on him. He is still relatively young, but the moment they say he's had enough, he will be found a good home. I would never race a horse just for my enjoyment, he has to want to do it - and be in good health as much as you can tell he is.
People forget that horses will stop racing when they have had enough and good trainers and connections will know when to call it a day. A good jockey will also be able to tell if the horses "heart" (excuse the pun) is no longer in it.
I was at Fontwell with Dave Evans and his son was riding one of his horses a few weeks back. Tony met us in the O&T's and said, he's had enough Dad - the horse was favourite but Tony pulled him up after a couple of fences. The owner was with us and said, fine - retire him. A decision made there and then by the jockey, the trainer and the owner. It happened last night at Southwell too. A trainer I know had a rather slow horse running - who ran... pretty slow. The trainer told me afterwards the owner had said if that's as good as it gets, find him a good home. The look of relief on the trainer's face was quite a picture. It can't be easy telling an owner sometimes that the horse is just not ever going to be very good. On the flip side, if you have a good older horse that loves his/her racing and the owner and trainer is happy to continue - and bearing in mind it's as expensive to train an old horse as a young one, then why not. No one can predict what a horse may die of and what's to say that an older horse is more likely to die of a heart attack than of a broken leg. shrug::