As a watch collector (ok, nut).. it seems to come as a surprize to most that watches have a somewhat limited life expectancy. Almost all the quartz (with some exceptions) watches are designed to last, at most, one battery change. They may last longer, but they are not jeweled movements. If they use the long life battery.. then the number of battery changes is "zero". Not that one cannot get lucky, just that they were not designed to last that long.
If you want a watch that never leaks.. get one of these:
Amazon.com: TechnoMarine Midsize MoonSun Abyss Watch #ABS19: Technomarine: Watches
As it is filled with silicon, if the seals fail, you would notice the stuff leaking out.. and without any air to compress, water cannot easily get inside...and changing that battery does require it to be sent in.
Regarding water resistant rating...
200 meters is the minimum level that one should get, if you dive with the watch. Any watch, with good seals may work, but 200 meter watches should have enough tolerence to allow for some seal degrading and still work (well, that is the industry belief anyway).
However, the normal leak point is the stem seal, from not being tight, or wearing out...as even a 50meter watch should be good to 50 meters when just out of the box.
I own two 500 meter watches.. and given the cost, would never consider taking them diving...