Gunman. Everybody to their own. So you are the person who gives me sleepless nights!
For myself, I would not use PVA for fixing or re-fixing a label unless it was a new and replaceable label in a new and replaceable case.
And even then, who knows the future value or rarity of items that we consider disposable now?
We are the guardians of our heritage and should try and treat everything as such.
I have to remove labels probably 10-20 each year in the course of scrapping or relining a case and I dread the realisation that a previous owner has used PVA.
I have a very good friend who is a highly experienced paper conservator, working for many years at THE leading London museum, and he shares my dread of PVA and other non-reversible modern glues.
They certainly have their uses but IMHO should not be used if reversible alternatives exist.
