how far do you walk in one day?

As some of you are aware, i am planning to do the Overland Trail next year, if i can get time off work, (or the year after if that fails). As i have not done a lot of bushwalking since i left the Army, i have been putting in some training. I am no spring chicken anymore and have started off short and slow. Thanks by the way, to all those who have responded to my myriad of questions about everything, i have made some good choices i believe in regard to what gear to buy and how to put it together.
Now, i am in Victoria and have started on the Warburton Trail ( the old disused railway line that ran from Lilydale to Warburton, some 37kms. It has now been converted to a walking/cycling trail) I live in Mt.Evelyn and have, complete with fully packed backpack, been doing slightly longer walks each week along the trail. i was knocked out with the flu for a while but have since resumed.
Now i did my first "lengthy" walk last week, starting at my place. Plan was to walk for an hour, turn around and come back. As the end of the hour neared, i was pretty close to the next station along the trail (some 6km from my house) so i continued on till i got there. Of course the coffee shop closed 10 minutes before i got there so i turned around and came back.
i had done just on 12kms, full back pack in the late afternoon on a day where the temp reached 35C. i took plenty of water so it wasnt an issue. I did have the "jelly legs" when i got home and thought maybe im not really up to this as 12kms a day is not unrealistic. But then i realised i had done 12kms almost non stop as opposed to doing it over a 12 hour period, which would be much more comfortable.
What is the average distance a novice and experienced walker would do in a day? and how long do you walk before stopping for a cuppa?
Now, i am in Victoria and have started on the Warburton Trail ( the old disused railway line that ran from Lilydale to Warburton, some 37kms. It has now been converted to a walking/cycling trail) I live in Mt.Evelyn and have, complete with fully packed backpack, been doing slightly longer walks each week along the trail. i was knocked out with the flu for a while but have since resumed.
Now i did my first "lengthy" walk last week, starting at my place. Plan was to walk for an hour, turn around and come back. As the end of the hour neared, i was pretty close to the next station along the trail (some 6km from my house) so i continued on till i got there. Of course the coffee shop closed 10 minutes before i got there so i turned around and came back.
i had done just on 12kms, full back pack in the late afternoon on a day where the temp reached 35C. i took plenty of water so it wasnt an issue. I did have the "jelly legs" when i got home and thought maybe im not really up to this as 12kms a day is not unrealistic. But then i realised i had done 12kms almost non stop as opposed to doing it over a 12 hour period, which would be much more comfortable.
What is the average distance a novice and experienced walker would do in a day? and how long do you walk before stopping for a cuppa?