As quoted from the CASA website
"A candidate may attempt any of the 7 subjects, as and when desired, to pass all subjects within 3 years (counting from the first attempt, successful or otherwise), provided the candidate has the pre-requisite qualification/s."
If its been 18 months, you would be getting close. The retraining periods I believe can be up to a month? Get in and get it done. Once you have the 7 exams completed, I dont believe there is any time frame to do the flight test? Anyone? Im pretty sure im right on that one.
Good luck with it!