IMO, the 2 on 2 off theory might be a waste for injectables; someone might want to concur. But, I wouldn't run that type of cycle for any injectables, not even with Suspension. If you run it straight through, the results are better.
You should run it for at least 8 weeks....trust me, you'll love the results. The tren will shut you down, but the prop will keep your libido up. When I do tren, I've always ran the test ester 2 weeks longer just to keep things safe! So if you ran the tren weeks 1-6, run the prop weeks 1-8.
If your worried about getting shutdown, then run HCG throughout the cycle....