Moved to NZ when he was 8 years old (1998) then appears to have signed for Ipswich U18 in 2008 so possibly 10 years?
Can't find any specific reference other than "grew up" or "spent his youth" in NZ...
EDIT: It's probably less - according to this, he signed his first professional contract in 2007, by which time he was already a product of the Ipswich YT - so you'd think he'd been there 2-3 years by that point.