Hyperdrol X2 was designed so that you will notice the effects right away. "Kicking in" is usually associated with long-esterified injectable steroids.
I would say sometime between weeks 2 and 3, you should have accumulated a significant about of mass and strength. I'm just finishing my first week, and definitely noticing increases in strength.
If funds permit, I'd definitely say pick up 2. 6-8 weeks of fun is more fun than 4 weeks.