This is Krispin, our 15 year old English cocker spaniel. He has slowed down, but only in the last 3 years or so. He was definitely high energy and headstrong. He is his own master. My dad raised him as his equal. He goes on walks without a leash, often goes to walk himself (small old-time suburb where everybody knows everybody). He is deaf now, but does not seem to mind one bit.
I would not get a cocker if you don't have much time. They are very social. In fact, to be direct and honest, I would not get a dog if I didn't have much time. It's not fair to the pup. Any pup. THere is no dog that will enjoy being alone for hours on end.