Your watch almost certainly contains an old type Kinetic capacitator which they found only had a 5 year life. Seiko have an upgrade which can be fitted at a Jeweller for about £100 or you can buy a kit on Ebay for £20 and fit it yourself (You have to be quite compendant in watch repairs to do this). The new component has a life of 20 years (or so they say!)
Depending on the value of the watch I'm afriad to say, it may be just as well to buy a new one!
Garyb
November 2010