Didn't we try a 12 month cycle 10 or 15 years ago?
Guess how they measure whether the training is effective? Failure rates. Yep, we don't have enough guys failing training in the the 6/12 model, so they can "afford" to stretch it out. It all comes down to dollars and until the correct percentage of pilots start failing, they will stretch out training to save money. They fail to see what happens if that failure happens on the last trip before the scheduled sim for a particular pilot. They also don't seem to care what effect a training failure can have on a career.
Most of us would think that zero failures is the goal, but not the accountants. This just serves to remind us all that we are a cost center, and an expendable one at that.