On a modern high pressure injection engine, I'd change them often. I skipped a year on mine because they are very expensive, $100+ for 4, but the service engineer bought one into the shop for me and showed how burnt out it was. I'd done less than 10,000 miles. I appreciate mine has almost double the power, but yours is a similar set up, small displacement, turbo charged, probably has high pressure injectors like mine too.
[B]Hi 'flag, Thanks for your input here. I'm now waffling between dealership plug replacement and using my MPG, easy starting and freedom from misfires approach........which has worked well in previous cars./B]
It depends on the type of plug you have fitted. My Jazz has the option of standard plugs changed every 25K miles and Indium plugs. These only need changed every 75K.
If you follow your routine it might be worthwhile removing, reset the gap and refitting them. It is too large a gap that can cause coil failure and plugs left too long sometimes seize which removing and refitting help prevent.
2006 Honda Jazz 1.2i-DSi S Vivid Blue Pearl