Last Combat Wedgie How Long Do Steel Toe Combat Boots Last And How Can I Make Them Last Longer?

How long do steel toe combat boots last and how can i make them last longer? - last combat wedgie

http://www.transworldsurplus.co.uk/images/products/invadr-10.jpg
I recently bought a pair of Invader Miltec 10 holes in the steel-toed combat boots.
They have steel toe and rear and screws in the sole, high quality cowhide.
How long they last, on average, and what I can make it last longer?