I have a Springer and a Cocker, both young. They get about 45 minutes in the morning, same route, they are quite chilled on this walk and will just mooch, as it is so familiar. Then in the afternoon they get at least an hour, always a different route (I have a few, to include woods, parks, lakes, fields) where they run, non stop, for the whole time 
DH does the walks at the weekend and will be out with them for at least 90 minutes both days, with a shorter walk.
Once a week they might miss the morning walk if I have to get into work early, and they are fine.
They also get a lot of training too, in short sharp sessions, we clicker train too. They also have interactive feeding bowls to work their minds and Kongs for mental stimulation.
They are both extremely chilled dogs, but they are probably getting their needs met.
Indeed, both have had injuries that have curtailed their exercise and they were both fine on less, but, for us, that's not the point of having spaniels, they come alive when they are outdoors and exercising.