I need to replace a battery in a Michele watch. Sometimes I am asked if I want the seal replaced which is expensive. DOn't i need that

Seals in water resistant timepieces go bad over time. This exposes the movement to moisture, dust, etc. which can damage your watch, costing expensive service or a new movement. If the watch is worn in the water often, the rule is to replace gaskets every 12 months. If it is occasionally worn in the water, they must be replaced every 18 to 24 months. The seals must be tested properly under the appropriate pressure for the rating of the watch by submerging the timepiece in a pressurized chamber. If your watchmaker is recommending this for a watch rated WR, water resistant, or 30M / 3 BAR don't bother. This should never be worn in the water. If it is for a higher rating (50M/100M+ 5BAR/10BAR+) and you wear it in the water, it may be worth the investment.