For starters, the preliminary paperwork, even if your employer starts the process immediately--and many don't--can take well over a year. In my case I was waiting 15 months before I gave up and relocated to Australia.
As for the time taken, my personal experience has been that PERM takes about 6 months. After that I-140 + I-485 can be concurrently filed if your Priority date is current. They can take another 6 months to get approved. After that there is a mandatory 180 day period before you can switch jobs. Total average case time should be around 1.5 years. This assumes that your application is not audited and your immigration lawyers are not backlogged. YMMV.
This is false. There's a lot of misinformation on the internet about this. Speak to an immigration attorney and you will discover there's no mandatory period whatsoever.
See also: Rights and Responsibilities of a Green Card Holder (Permanent Resident)
http://www.uscis.gov/portal/site/uscis/menuitem.eb1d4c2a3e5b...
", the approval of a Form I-140 employment-based (EB) immigrant petition shall remain valid when an alien changes jobs or employers, if: • A Form I-485, Application to Adjust Status, on the basis of the EB immigrant petition has been filed and remained un-adjudicated for 180 days or more; and • The new job is in the same or similar occupational classification as the job for which the petition was filed. "
[1]Policy and Procedural Memoranda on the American Competitiveness in the Twenty-First Century Act of 2000 (AC21)
http://www.uscis.gov/USCIS/Laws/Memoranda/Static_Files_Memor...
And my wife is Aussie so getting Australian residency was straightforward.