It's not a bad idea, it's actually a good idea in my opinion.
We get ours as soon as unconditional so that we can vary our PAYG withholding more accurately.
ATO + employers payroll takes about 2 months from when we submit until it takes effect, so it pays to get it done ASAP.
If you're just guessing on the depreciation figure, it means you have to make up for it later. There is enough guessing as it is when it comes to the other figures and projections. Doing the PAYG variation with exact figures at least for depreciation is much better.