Exactly, a lot can happen to a vehicle in 6 months! Same with new vehicles not needing to be inspected at all for the first 5 years, a sales rep's car could have half-a-million kms on it and have been smash-repaired a couple of times by the end of 5 years.
Getting back to pink slips, many years ago it was 14 days, then they increased it to 30 days, then again to 42 days and now 6 months. I reckon they're slowly phasing them out myself? And not before time either, NSW has been the last state with yearly inspections for a long time now, I think the ACT was the last to get rid of them and that would have to had been 10 years ago I reckon?
I've read that politicians are in favour of abolishing yearly inspections (because there's votes in it for them to be able to save the tax-payer $50 per car per year, money that doesn't go into the govt's pocket anyway) but the unions and motoring organizations are against it.