Expiry of watch pairing to a google account

If I pair a Galaxy 4 or 5 watches with a phone, but then the phone is not available, the android user is still set, and the watch can still get updated with Google Play - as long as wifi is connected.

My question is if this is forever, or if the phone is away for X days or months the user will get discarded?

I have a system with smartwatches running an application standalone, and we intend to pair them to the phone only for the initial installation of the application from the store, but than the phone may not reside in the same site anymore.

You may want to ask Play Store this as I have not first hand knowledge but…
I traded in my Watch4 for a Watch5 nearly 5 months ago and it still shows as my device in my google account.

If the watch is paired to a different phone the app will be removed, that does a factory reset when first paired.