My questions is how important and how many take the proper time off between cycles. From my research if running a 12 week test E (500 ml per week)only cycle you wait 2 weeks to start PCT and that runs for around 4 weeks. That gives you a total 18 total weeks on. I've seen people say you should wait 18 weeks before next cycle. How many actually wait the 18 weeks.

What risks to you run if you don't wait the full 18 weeks?