Why do our A7750's need a service? Because we are too cheap to buy the gen which comes with a warranty. If you don't care about the brand name buy a no-name or lower end branded watch with the same aesthetics and with a warranty.
Seriously, unless you take your watches apart you will not have any idea what condition your movement is in, whether it was properly serviced (unlikely), if and when it will stop running properly and when it does whether you will be able to get the spare parts. So it will always be a guess unless you go to the trouble to break down your movement when the watch is received. I do subscribe to Freddy's theory. Decide whether the watch is a keeper before investing in a service.