gtseraf is absolutely right in his response and I will add what I responded to the same question on APC forum today:
The Command evaluation process has changed recently, but as far as I understand when your number is up (right now about 3-4 years in company) you will get evaluated. 4 times a year a small group of 4-7.
I think that there is a sim now ( a LOFT, I think) and you fly 5 or 6 regular trips in 2 months with an Japanese instructor/checker and they ask you questions and look at your flying and management skills. After all in the group have completed the evaluation, management have a meeting and they decide who will go forward and who fails.
If you pass, upgrade sim training starts within 2 weeks, if you fail, it depends. Some have been evaluated again in 6 months, some in 2 years. It goes case by case.
As far as the fail rates go, it used to be about 1 or 2 failures a year for 16 candidates. Recently looks like 50% failure on evaluations.
There are many reasons for this:
( I know I will get comments about this, but...)
some are not mentally ready for it, some lack the knowledge (not enough study), some don't have the right attitude, and some just need more experience. I had a conversation about this recently with a checker who was involved with the process and that is what he told me, adding that some will never upgrade.
It is not an automatic thing or an entitlement here, you must put in the book work, show the right attitude and eat the **** for a while. Once you are all done, its a great job, they leave you alone, but the whole progress to get there truly sucks
Hope that helps