You're to be commended! There is no point in having a GHB if you can't make it home with it. The only way to be sure is to do a trial run.
By the way I do this every day. I live a mile from work and I walk it even in the rain (USGI Poncho for the win!). The only time I drive in is on Sundays because parking is free that day. I always carry my GHB, which is in fact my BOB and weighs 50lbs! Twice a week I take "the long way home" and carry it for 3-5 miles in order to be prepared for longer hikes. These longer treks leave me exhausted, and I need to rest at leat 1-2 hours before I can start off again.
As I suspect is the case with many people here, my GHB/BOB was overloaded at first, and I could barely drag it one mile. I even had to take it off and sit at the side of the raod for a few minutes before continuing on. People in cars slowed down because they thought I might need medical attention!
Another time after overloading my backpack I was only two miles in to a three mile hike when my calf cramped up and I looked like Frankenstein spasically limping the rest of the way home. You can physically incapacitate yourself if you aren't realistic about your capabilities by practicing. If it happens in a crisis you're royally screwed.
So after these harsh, embarrassing lessons I shed a ton of gear and gradually, as my strength and endurance increased, I could add more and more gear back into the backpack, and walk farther and farther each day, until I'm now finally at the point where I can confidently carry my fully stocked BOB 10 miles in one day. No way could I go farther than that without ditching equipment or training harder and more intensely.
I'm 50 years old and am only in average shape. If I can carry a 50lb load for 4 miles at a stretch without resting, on a twice-weekly basis, anybody can. But it only becomes possible with practice, which frankly can often be an unpleasant, tedious excersise. However if you want to carry a lot of stuff, which most of us do, you need to do these trial runs or else you will fail miserably when a real, serious, and potentially deadly crisis forces you do get home or bug out on foot.
If you don't practice, your GHB is merely a ball and chain. It in fact becomes a "Never Getting Home" bag. And your comforting self-delusion about how far you'll be able to walk in one day becomes a dangerous fantasy.
"There are a lot of things I've been blamed for that I never did. But then there are a lot of things I did and never got caught at." ---Johnny Cash---