You'll get people that will tell you that it's possible to recover after years of being on, and you'll get people that will tell you there's always a chance that even a few weeks on cycle will make you need Hormone Replacement Therapy (HRT) for life
I think that if there's nothing wrong with you, you should be able to get away with a relatively long cycle. But the question is, are the side effects worth it? If it's your first cycle, I go with 10-12 weeks