Mine is in the medium energy range. If I had been younger and fitter, I'm sure she would accommodate and gear up. I'm your age, but I never thought the dog would be too much for me. I know she'd like to be out more, but the weather is difficult. Generally she gets a couple of walks per day, but snow and treacherous ice conditions mean going for play dates with her cousin dog. She loves wrestling with the Rottie, but it doesn't make up for fresh air.
She loves the dog park, and is amiable with almost all dogs. She tends to find dogs her own age and size for playing chase. It is rare for her to dislike a dog (she even loves the small ones, and is generally very gentle with them.)
Big bed hog, couch hog, constantly hungry and on the prowl for edibles. Huge personality with a highly developed sense of what is fair:. I'm not kidding. On the three occasions when she was physically punished, she sulked and vocalized with "woo-woo" sounds. She'll retreat to the stairs and refused to come to me, all the time "woo-wooing" at me and tossing her head and throwing her paws out in complaint. It's a very heartfelt recitation of the wrongs done to her. (Very funny, but hard to keep a straight face.)
She will punish me if I upset her, ie., she was upset about our return to work after a lovely two week vacation. The first day she dragged my clogs into the living room and chewed them half heartedly. The second day she dragged my clogs and running shoes into the living room and she pulled out the inserts. The third day, she took the clogs, two pair of running shoes, pulled out the inserts, ripped them up, chewed one of the heels and ripped up a flyer. She was lectured the first two times and had to listen to me yell. The last time she got four smacks with the destroyed running shoes, and she retreated to the top of the stairs to lecture me with her pathetic "woo-wooing.".
All in all though, she is a wonderful and obedient dog that will do anything to please you. She needs to go to obedience training, as do most large dogs, and her intellect would benefit greatly from the stimulation of some specialized hunting or searching training as she has a great nose. She is protective of the home, but there isn't an aggressive bone in her. I'm not sure what she would do to an intruder unless we were personally threatened. She's very mellow. The mother was great with visitors, but would protect the perimeter....you had to be welcomed in before she accepted you.
Fully grown, they are very impressive and fearsome. I love that my dog's ears and tail were left natural. She's very beautiful, I don't need her to look scary...her size is enough to deter most people of evil intent.
Oh, they are big snuggle bunnies and love to be close and be touched often. Mine loves snuggling on the bed (get a big bed!)
