Personally, I do believe that the overall level of inherent safety is depleted by the cadet recruitment programme at many European Airlines if it is coupled with a regime of early command upgrades.
What's an early command upgrade?
Pilots nowadays work a lot harder (more sectors, more hours) then they used to, ergo you build up experience faster. I would not be surprised if a 5 year pilot will have gained as much hours and experience in those 5 years as a pilot would do in 10 years in the 80/90's.
5000 hours flying longhaul into major airports with ILS facilities and long runways, does not generate the same experience as 5000 hours shorthaul to a greater variety of airports that also include non-precision, circling and visual approaches.
As long as you are not fatigued, continuity of flying will make you a better pilot.
Not a single commander will have experienced everything before he gained command, and statistically you never will. It's all about the grounding, selection and attitude of the command candidate. Hours or indeed time in the airline are a very small factor.