Earlier quoted context omitted.
Replace the laces with 2-4mm bungee cord and you are set for life. That was a pretty common trick for combat boots before the laced + side zipper boots became more popular.
What's the steepest decline you've walked with that setup? Did your toes touch the end of your boot?
You don't tie as you would normal laces you create a knot on one end and loop it through all the lace loops then you simply pull and loop it around the shaft and the colar and tuck it in it was secure enough to even run in (as much as can one run with a full kit and a PRC-77 they had us chugging along during training) and traverse any terrain I had too.
I don't know how would if fare in very cold (as in sub zero) weather but then I had normal laces snap on me while trekking in Peru and Iceland as well.
BTW don't forget that while a bungee cord can stretch pretty well the shorter it is the more stiff it is so all of the bends in the loop essentially create a lot of short individual links that don't stretch as easily as the entire length of the cord unwound, you also need to overcome the friction between the cord and the tongue of the boot which makes this setup pretty darn secure but easy enough to pop on and off if your curl your foot and ankle and ease it in or out.