A good pair of work boots is a $250 tool. You wouldn't leave a Milwaukee impact in the rain, fail to charge it, then complain when it dies on you in nine months. Same logic applies here. The boot is the tool. Treat it like one.
Rule one: have two pairs and rotate them. Leather needs about 24 hours to fully dry between wears. If you wear the same pair Monday through Friday, the moisture from your feet never fully leaves the leather. The fibers stay soft, the stitching weakens, and the inside breaks down before the outside does. Two pairs costs more up front. Both pairs last roughly twice as long. Math works out.
Rule two: dry them right when they get wet. Not in front of a heater. Not in the dryer. Heat dries leather too fast, the fibers cinch up, and the boot cracks across the flex point in the toe within a season. Pull the laces all the way out, pull the insole out, stuff them with newspaper, and put them somewhere with airflow. Change the newspaper at hour four. Done.
"The boot is the tool. Treat it like one."
Rule three: condition the leather. Once a month if you're outside in the weather, once every two months if you're mostly inside. Mink oil, Obenauf's, Red Wing's leather conditioner — all fine. The point isn't which one. The point is doing it. Dry leather cracks. Cracked leather lets water in. Water in the boot kills the boot.
Rule four: get them resoled before the welt is gone, not after. Goodyear-welted boots — that's most Red Wings, Thorogoods, the better Carharrt, Wolverine 1000 Mile — can be resoled three or four times if you catch them in time. Wait until you've worn through the welt itself and the resole costs more than the boot. Look at the rand where the upper meets the sole. If you can see threads, it's time.
Rule five: replace the laces and insoles before you replace the boot. A $12 pair of insoles and $4 laces will make an old boot feel like a different boot. The leather is fine. The footbed isn't. People don't realize that's why their boots feel done.
And rule six, which is really rule one again: don't wear the same pair every day.