I've seen plenty of fitters doing that, so I suspect it's probably safe.
However, when customers have suggested it to me I point out:
1. Glass becomes more brittle as it ages - UV exposure and repeated expansion/contraction cycles.
2. Did the fitter use the correct 6" bolt that he'd left in the van or the 2" screw he found in his pocket that would be invisible a moment after he'd used it?
Vin