dutchsiberia wrote:About the gasket, I changed the battery a few times on my actively for diving used Citizen dive watch and it remained waterproof. Be careful not to damage the gasket and keep it spotless, very ligthly lubed with silicone grease. At your own risk of course!!!!
I also have change batteries on Casio / Timex for many many year with no issue
As long as the condition of the gasket is good, and you set it correctly without damaging it when closing up the caseback, you shouldn't have a problem.
Beware, I only go pool deep with my watches, if you dive, then definitely do pressure test and have the gasket replace every few years.