
I have four dogs ranging from 3 - 13 years old (sighthounds and spaniels) and luckily all of them are well and even the 13-year old still keeps up easily with the rest of the pack, so I don't have to do any separate walks with any (yet).
Mine all get one walk a day, though we also have a big garden where we play and train, it's big enough to have a bit of a run too - even for the long legged sighthounds. (I too bought the house due to the garden for the dogs... LOL).
During the week I take them out for an hour before work, about half of that off lead (2 of the dogs)/long line (the other two).
At weekends we go to a different area for 1.5 to 2 hours where again about half is off lead (three of the dogs) and one on a long lead (though working on getting him reliable enough for off lead too). Where I live now in the countryside we rarely meet any dogs, so that isn't really an issue anymore - but lifestock and wildlife now is, hence why I have to be very careful where I let my high pray/hunting drive dogs off lead. Previously in London, I used to walk in either areas where I had a good view around me or at quiet times to manage my lot around other dogs. Here I have to pick the areas and times depending on the lifestock and wildlife around us.
They also go to training classes weekly (or will do again when I have found some in my new area) and the younger ones to obedience shows at some of the weekends.
When I used to live in London, they had a bit more off lead (same amount of exercise but more of it off lead) and more socialisation with other dogs, but the garden was so small that it was unsuitable for anything other than toileting.