(Concern) Loss of retention device after orthodontic treatment

I had a fixed retainer after orthodontic treatment 15 years ago.

A few years ago, some places that were fixed fell off.

I can't visit the dental clinic immediately for correction.

I was living in a fallen state, and the retention device completely fell out.

Should I visit the corrected dental clinic again to have the retention device attached?

Will my teeth shift a lot if I don't use the retention device?

Do I have to wear the maintenance device for a lifetime?