I don't have any reseach data, but from the coal face we often flew those who had minimum hours, those looking for a job, and if they had not flown for an extended period say six to eighteen months, then the first hour they flew was often quite good to immaculate but their standard deteriorated drammatically after that most often to a point of being seriously dangerous.
Of course from there they went into a dual training type program where they oftem flew as many as 150 hours dual before being allowed solo to do specific tasks.
We had three benchmarks from that intro, they first graduated to 'ferry standard', where they could be trusted to navigate and fly above 500 feet with a reasonable chance of landing if something went wrong, then they went ont what we called 'survey standard'.
This meant excellent skills in confined areas and much better at autos including an introduction to Low level autos.
That would be around three to six huindred hours. ( no one can do this nowadays as nearly all boss geos requires a min of 1,000 hours for their contracted pilots)
If they survived their first couple of hundred hour jobs at that. or mpre to the point our nerves survived it, then they would be inducted into the 'mustering standard' and taught specifically how they could be bitten with being caught turning downwind and of course heaps of commercial types tricks.
Usually they had gained around 1,000 hours under supervision, I.E. often flying solo in dual musters rather than as dual in the closest sense before we would be game to let them out on a solo muster, where they could meet and beat most challenges, come home without wrecking rod ends on the aircraft and keep the clients happpy.
Ther most dangerous level in their career was from 800 to 1200 hour mark as that is where they had learnt to manipulate the machione easily and often did so without regard to the cattle or their maintenance bills.
There were two types of check flights in that area,
1. Was for the cautious types (about 92% of the individuals) who wanted to learn more about their maneuvres and machines and where it might really bight them, and
2. was for the 8% just way too flamboyant types who really 'got it' and came back from that taken down a peg or three.
From there they usually accumulated up to about five thousand hours before we could consider them crash proof and excellent aricraft operators.
Those guys are now flying all around the world and doing well, I can say with some pride as to having been involved along with the chief pilot, managing director and especially the senior workshop staff in directing them along the way.
However we have often come across individuals with anything up to 2,000 hours or more who have not flown for say six mionths and do way too dangerous things, like move outside their comfort zone and crash an aircraft by overpitching at low level maneuvering.
From my point of view the simple BFR requirement is ridulous, regardless of their experience up to say 2500 hours they should be required to do a few hours dual before being signed off and much less above that hour mark as by then they have learnt usually to temper themselves and stay indie teh comfort zone.
I think it might be up to the operator to work out what comfort zone he requires as to do a simple five or six hours ofd check rides with a couple of IFR approaches mighht be tempting fate way too much.