Very much agree,Tilly.
I think a minimum 3 years if you're on s/haul or mix of long and short as with UK Charters.If you are L/haul only,with only 4/5 trips a month or so then I'd go for minimum 6 years.There is no substitute for "experience" regardless of how confident you may be.You need hundreds of flights under your belt to fully understand and be able to deal with the vast array of situations,problems and scenarios that crop up all the time even on the most normal of flights.
I am not a SCCM,but have flown for a couple of airlines over the last 13 years.I need to feel confident in the abilities of my SCCM when on a flight.Their age is of no concern to me,but I their "experience" certainly is.