You don't think the 'stretching' of a horizontal unsupported length of 8m is damage enough?There is perhaps another issue.
I personally very much doubt that T+E of any size would, per se, be damaged 'due to it's own weight', even if it were an 8m horizontal run. However, given that neither back boxes nor accessories have any 'strain relief', there could be an issue in relation to that if the weight of unsupported horizontal runs of cable were trying to pull the conductors out of their terminations.
Kind Regards, John