My house has about 35 circuits, across about 8 CUs - I wonder how you would classify that?
In the case of a 1,000-circuits factory (or even my house) what is a 'big time saver' is having access tio good documentation of the installation. If one is going to undertake the current I&T properly, I can't see how/why knowledge of previous I&T findings will (should!) make one's current task any easier. As I'm said, after one has completed one's inspection and issued a report, one should then look at any previous reports/information, and then comment on any significant changes/differences if necessary.
As has been said, one of the worries (particularly for domestic installations) in the hands oif of 'black sheep', sight of a prior report could be a massive 'time saver' - since, rather than doing any I&T, they could simply copy/paste (with some slight changes, if they were 'sensible') from the previous report!
There is probably one complication in relation to the commercial stuff. Somewhat to my surprise, previous discussions here have suggested that EICRs on large commercial installations may only be undertaken on a relatively small proportion of the circuits. If that's the case, it is obvious important to know which circuits have (and have not) been previously looked at -since, otherwise, some may never get inspected. However, again, there is no need to know the results of previous inspections until after one has reported on the
current condition of whatever has been inspected.