It has to be said though that thousands of BG's have been TT'd presumably successfully.
Bottom line is that no matter what BG you have, its a gamble just how long the artwork will remain on there - variables like humidity, temp change, scratches etc all speed up its demise. If a BG is flaking or lifting, its on its way out and TT will prolong its life quite a bit.
Are some BG's better than others? Well...yes, even off the same model game - one BG will outlast another - depends on how clean glass was at manufacture, composition of inks etc - A print off one day may last 10 years longer than a print off the next day - its just the way it works.
 The European prints tend to be much better quality than US ones - a Segasa BG will have survived over the years looking far better than a Williams, Gottlieb reds are a problem etc etc etc.
I dont use TT, i dont touch a BG with anything unless i REALLY have to.
Yes the guys BG is ruined, but was it really necessary to TT?

If a BG is going to flake - its going to flake... what i do is watch the amount of flaking - normally starts at the bottom. Mark on the BG just where the flaking ends with a dot from a marker - if it goes beyond this, its dying a slow death and needs to be sealed. Chances are though that it may never go beyond the mark.. it may not flake any further... its all down to how well its adhered to the glass in the first place.
if you are going to seal then do it in light coats - allow to COMPLETELY set before the next coat - dont go doing it in thick amounts straight off.

The idea is to have the paint stuck to the glass, if the TT or whatever is used is thick and sets then any slight shrinkage will just pull off the artwork - after all something has to give, with light coats, shrinkage is at a bare minimum... and NEVER try to speed up the drying process, slowly but surely is the go