Check your horse daily to make sure that the blanket is not rubbing or pulling. Broken hairs are an indication of chaffing.
Fold the blanket properly to make putting it on and removing it safer and easier.
In some areas you may be able to find someone who does horse blanket repairs exclusively to get some extra life from a horse damaged rug.
If your horses are outside a lot it will be nessesary to have two outdoor rugs. When you have many days of heavy rain then even the most expensive blanket will saturate over this long time. An extra blanket means you can switch and allow one to dry.
Don't try to wash your heavy outdoor blankets in the washing machine. Most are too heavy when wet! Either send them to a blanket cleaning service or go to work with a scrub brush, mild soap and garden hose or power washer when the weather is good.
If your blanket is loosing its waterproof abilities try a spray on waterproofer. Your saddlery can advise on products available.
Some horses like to play 'rip the blanket' and will destroy their own or a paddock mate's blanket. Try bitter spray-on products made especially for horses to discourage this type of play. Try providing other toys like play balls and old jeans with the buttons removed if you have a horse that likes to pull at things.
Horse rugs have a hard life from the horse that wears them, other horses in the paddock, fences, trees, travelling, the weather and everything else that goes on. Fortunately rugs are also very repairable and most damage can be repaired by a good rug repair service. Your local saddlery should be able to recommend a good rug repairer.
Properly rugging your horse will help maintain condition and weight and reduce feed bills. When a horse is cold it will eat more food and burn energy to maintain its body temperature.