The last guys in seniority in my class got no time off between ground school and sims. Your class might be different though. Some of the guys with the highest seniority wanted the sims starting the next day and some wanted the 3 week break. If you are bottom seniority you just get what is left over.

From day 1 of indoc to finishing IOE, you can plan on about 2.5 - 4 months, depending on lots of factors.