If a leather bag shows signs of drying and cracking, seek assistance from a leather care professional. But before that happens, invest in a leather conditioner! Since leather is porous, it loses moisture through evaporation. Use a conditioner once a month to keep your goods looking their best. Wipe excess product and allow the bag to air dry completely before storing it.
You can apply a water and stain repellent product after conditioning. These come in direct application or spray types. Follow the manufacturer's recommendations for these products to avoid leather discoloration or damage. Application-type products last longer than spray products. If you choose a spray product, remember to reapply it regularly. Bear in mind that this provides some protection, but does not make the leather completely waterproof.