No other type was less than 5yrs 6 months and none longer than 7 years.
I know old beggars have said similar before, but I was commissioned 7 Jun '68, and "operational" (ASC C Cat at the time) 28 Sep 71 - I make that about 3 years and 3 months. (if you count a D Cat it was less than 3 years) SH Wessex as it happens; those who had the (mis?) fortune to go to Whirlwind Sqns could probably beat that. Even then FW and (particularly) FJ was lots longer.....