Clean your watch as often as possible. At the end of the day when removing your watch, use a soft cloth to wipe any residue or fingerprints from the case, crystal, and strap. Rinse your watch under fresh water regularly to remove any sediment that may accumulate while wearing it. This is especially important if the watch has been in contact with chlorine or salt water.
The longevity of a leather strap depends on the user's wearing habits. All Mondaine leather straps are made with genuine leather, which can be damaged by excessive moisture. When possible, avoid wearing your leather band in water, whether swimming, bathing, washing dishes, or any other water activity. If frequently exposed to water, sweat, and chemicals, such as cleaning supplies or perfume, the strap will weaken and wear out much more quickly. It is also recommended to regularly change out the strap for hygienic reasons.
Keep the original box your watch came in for storage or purchase a separate jewelry box to store it in away from your other jewelry. This will offer protection from dust and scratches when you're not wearing the watch.
It is recommended that you have periodic maintenance services by an authorized Mondaine service center. You should never open the watch yourself, as dust and other particles can get in and ruin the movement. Leave all battery changes, repairs, etc. to the professionals, just to be safe.
Most importantly, make sure to read your watch manual to know the specifics of your watch model for proper care.
Find warranty information and the U.S. service center contact here.