How long can a car sit unused before the engine seizes up?
My brother-in-law has a VT Commodore and hasn't used it in 4 months because it needs fixing (no idea what's wrong with it). I'm worried that he's left it too long to fix and now he'll need a new engine.
You would worry more about oil seals drying up in the tranny, power steering, water pump and valve cover gaskets. Then they start leaking.