There are two types of leather found in furniture today – treated (aniline dyed) and untreated (natural leather). Each type of leather requires a different method of care. Treated leather goes through a dyeing process where protecting chemicals are added along with possible color dyes and optional lacquers to add shine. The chemicals add protection which increases the life of the product and the amount of wear and tear it can withstand. Protected leather will not be darkened by liquid spilled on it unless it sits on the leather for longer than 12 hours. You should never use mink oil, saddle soap, or car leather care products on protected leather. These products are not designed for furniture. There are products on the market such as Leatherique and others that may be available at furniture stores that will be safe. There is not a requirement on how often to moisturize leather. The best thing that you can do is to dust it often, keep it out of sunlight (UV rays), and clean it with a soft damp cloth if needed. I would not suggest moisturizing more than once a year.
Natural leather on the other hand is not treated with any protecting chemicals. This leather may have unique color patterns and varying grain patterns upon close inspection. Usually high end furniture is made with natural leather due to its high costs and competition for it among products such as designer purses and shoes. Cleaning agents should never be used on this type of leather. The moisturizer/cleaner will soak into the leather and create a patina, which is a darkened area. Many pieces of furniture have been ruined by cleaning/moisturizing products causing leather to darken, and no longer match the decorating colors of the home. Natural leather should be dusted at least monthly. Avoid using a damp cloth at any time, but if you need to clean something up, do so by all means. Be very careful of liquids since natural leather is very porous and will absorb the liquid quickly. Natural leathers tend to darken a bit as they age due to sunlight and the natural oils found in human skin. Sunlight is very bad for natural leather as the exposed area will darken.
