Its already worth a small fortune in mint and complete condition. But I personally would never use digital watches as an "investion", its a reliable watch, but there is always a chance of something getting broken after so many years.
The value of vintage digital watches increases from year to year, but so do inflation and chances something gets broken. :wink:
It will always stay pretty collectable I think as its one of the first LCD calculator watches and there are also many people collecting Seiko digital watches (especially japanese).
If you want it as a collector, then buy a cheap used one without box/paperwork and you will most probably have a stylish nice watch for many years.
A real "die hard" collector would of course want it in mint condition and never wear it. But you didnt sound like one of these to me. :wink: