Whats the chance of burner damage due to overwriting ????

As overburn generally comes as a 'feature', I wouldn't imagine any problems. If a burner is not supposed to overburn it just won't do it.

From experience, when an overburn process fails, all that happens is that the lead out fails, whether this in itself causes damage to the lens.......

I don't think that you will find one member here who has damaged a drive from overburning, but plenty who have overburnt sucessfully many times over (including me with several drives). That said, if you do damage your drive overburning then it ain't my or anyone elses fault, hence all the warnings.