4 weeks may seem long but keep in mind it takes 150 mg of clomid to produce what 20 mg of novadex is capable of, ......but with a milder drug like primo you can use the milder SERM clomid you to taper your PCT and bring your body back on line smoothly with little down time. You could probably skip the 4th week but I found this 4 weeks to work great, no crash at all and strenght stayed relativley high. Not as high as the cycle but stronger then when you started.
Basic PCT's are around 2-3 weeks and Anthony Roberts advanced PCT is 6 weeks I believe but these are also for 8-12 week cycles. I think If you spend the $$$ on 16 weeks for a designer like primo you want to maintain those gains, so 3-4 weeks isn't unreasonable espesially scince you're not being absurd with your doses and the products dicused are some of the mildest you'll find as far as toxicity goes.