All rifles that got an FTR on them saw heavy use, that's why they saw refurbishment ... Factory Through Repair. Many rifles that went on to be sold into civvy street would never tell you how much use they got since in the instance of Base Repair or Unit Repair workshops, there was often little more than an R/Date stamped on the butt stock ... if they got that at all. Many stocks have been sanded since then, so more evidence would be removed in that effort.
There were of course in times gone by releases to sale of store held No5's that were from like new to refurbed. The point being that the No5's that the Indians, Pakistani's and Malaysians held for service were left to them by the Commonwelath forces ... so not only had they seen late war action in WW2 many of them ( Burma the main theatre ) but then many saw service in any number of small wars and counter insurgencies in their parts of the world since ... add to that duty in Military and Police capacity. This is all before they even hit civvy street for sale ... so I would say the rifles in peoples hands today vary from store refurbs to units that saw heavy use and were then sold out of service having reached their serviceable limit.
The most common thing on a No5 rifle is a worn barrel ... most of them. That alone tells you the rifle got heavy use ... if you find a No5 with mint barrel, you very likely got one from store. Mine was filthy when I got it and I managed to get it to clean up, I also bought a brand new spare No5 barrel in the paper ... always good to have a spare!