Hi Roses, we have four senior greyhounds at the moment, and have owned/fostered more previously.
Not directly a suggestion, but may i share a little story with you? About seven years ago, we had our first oldie, who had arthritis. Up until then, I'd previously been an owner who had just accepted that getting old meant stiffness, poor QOL, incontinence, forgetfulness etc. Our then vet completely changed my way of thinking - it was a real paradigm shift moment. He was really passionate about older dogs and especially their quality of life, and challenged me at a very deep level about my thinking/approach to how we managed her care. Instead of simply accepting some quite serious issues hampering her quality of life, he encouraged us to think hard about how we could together improve and maintain her QOL. This is in no way to minimise the ageing process, and I would never advocate keeping a dog alive for instance who is in pain, but I have come to believe that in general terms we are often too quick to accept outcomes that can be quite markedly improved with appropriate care. We knew that we could never cure her arthritis for instance but I wanted it to be something she died with, not died because of if that makes sense.
Since then, I've developed my interest in the care of older dogs and am very lucky to have several friends also involved with rescue who are also passionate about/experienced with oldies and we spend many happy hours discussing care and how it can be improved.
The biggest thing is your relationship with your vet - they should be a trusted professional ally. You know that old saying about how a year in human terms is seven dog years - would you let a 80 year old relative go seven years without a checkup at the doctor? You'll probably have an annual check up anyway but with a senior dog (say, 10 plus) I'd be comfortable with checks more often. For this, I'd go through every aspect of their care including diet, weight, exercise, sleep, living conditions, lifestyle etc - has anything changed? If so what, and how much? Looking at the dog itself - consider things like skin, weight, eyesight and hearing, teeth (big issue in greys - our 10 year old had her last four teeth taken out on Friday), appetite, mobility, any changes in muscle tone, etc.
Example - our 10 year old grey just before Christmas - her breath suddenly started to smell and I could see one of her teeth was discoloured. I could also on closer inspection see what looked like a small ulcer in her mouth. Took her to the vet - straight onto ABs and painkillers for the immediate festive period with a GA booked after the holidays. That led to all 4 teeth coming out but what it also revealed was that there was a big abscess that had actually formed a fistula into the nasal cavity - no wonder her breath smelled. 
Many people accept poor teeth and bad breath in elderly dogs without thinking about the pain and other health problems they could be leaving untreated.
Anyway, mini essay over. Apologies but this is something I am really invested in (as you've probably guessed). To summarise, back to the vet, consider each issue in turn, don't be afraid to ask questions, discuss, research, and do everything possible to work in partnership with your vet to create a great life for your two amazing hounds. In general, greys and lurchers are actually very healthy compared to many other pedigree breeds and the problems they do have are often related to consequences of their previous working lives.