Hey bro, I run long cycles like you. Time off is necessary for a few things but you need it to make solid gains that you are going to keep! I cycled too much and too long the previous 2 years and coming off was and continues to suck (anyone will tell you that).
Blood values get fucked up the more you use. Recovery is necessary, do more like 8 weeks. More would be even better but I know it is hard. Maintain PCT and be honest with your doc. Get hormone, lipids/liver function, etc.
I will say I have run 18-20 week cycles for the last 2 yrs with 6 weeks off and I am in good health but I am going to do things different. I am also, or was a pro athlete so that played a role!