
I have a GR and his main walk is around 4-6 miles a day, which is all off lead - only on his lead leaving the car and returning to it from the woods. We do this whatever the weather and every single day. He has only missed 3 walks in almost 3 years due to circumstances that just couldn't be avoided. I usually do one long walk and another much shorter one at some point in the day and also daily playing and training.
He never stops running around whilst walking off lead and probably covers three times the distance that I do but is perfectly happy and chilled out indoors. He is a total mud magnet and will swim in any water he can find - the sea, ponds, streams, water filled ditches. He always returns home very muddy but seems to have a teflon coat as the majority of the mud just falls off on the tiled floor and is easily cleaned up. A daily brush removes any mud that sticks.
He has a wonderful temperament, is easily trained and is a great companion. He rarely barks and is a very sociable dog. He does dig in the garden although this is getting less as he gets older - coming up to 3 years old now - ate all the shrubs in the garden as a pup. Great tumbleweeds of hair are a daily occurrence but are easily hoovered up but clothing always has evidence that you have a GR no matter what you do or wear :)
Other things to consider are the size of car that you have - GRs can take up a fair bit of room in a car and of course a large breed dog will cost more to feed and in vets bills than a smaller breed.
I love having a GR and would not want to be without one. We also have a small dog whom, although cheap to feed, treat at the vets etc is so much harder work than our GR and I have decided that I wouldn't have a small breed again - as much as we love this one he will definitely be the last small dog we have and the next dog will be another GR.