If you are right handed, the glove in your right hand will wear out faster. If you are left handed, that in your left will do. This is because the glove in the working hand is used more and so tends to wear out faster. To increase the life of the pair, keep changing them between your hands on different days.
When done with a gardening session, dust off your gloves well. The dust particles trapped in them tend to cause creases and tears. Wash them in a tub of non toxic detergent with your hands once in a while. This helps prevent tears and wears and also restores their suppleness.
When you are not using them, store them in an unfurled and flat manner. If they are curled up, the creases may develop into tears. Keep them in a place where there is no pressure on them. Use a clothespin to keep them together to avoid losing a pair. Designate a special storage area for them so that you know where your gloves are.
If a glove shows tear and by chance you own a lonely pair of another glove in the same material, you can cut out a piece and repair your gloves doing simple patch work sewing. This will extend the life of your working gloves.