ok, i found this in web, seems if me using 10000 it should be ok
If you plan to publish your application(s) on Google Play, note that a validity period ending after 22 October 2033 is a requirement. You can not upload an application if it is signed with a key whose validity expires before that date.
If you really want to see your key's expiration time though, you can use keytool:
this "Google Play App Signing service" looks like much effort/more time-consuming and complicated.
i will try a bigger validity first and hope we get this app in store this week.