One year if you're lucky
all depends on when EB2 becomes current. See time breakdwon below:
Preparing for Job ad: one month
Posting job ad: one month
Quiet period: one month
PERM Application: one to three month
preparing for 140: one month
140 Application: two to six month
Assumming EB2 becomes current before your 140 got approved, there goes your one year already.