10 is okay i guess, but preferably 12. i've used cyp a number of times and once in awhile i start to stall out around 10. all that means is you need to eat more... just fyi.
It really depends on how your body reacts. Myself it takes me 3-4 weeks to start seeing the full effects of test E (or C) so I run for 10-12 weeks. But 8 weeks should be fine as long as your dialed in.
I never make gains past week 8 after week 10 im always ready to stop like my body knows it needs a break or something... the sooner you get off the sooner you can recover and start a fresh cycle though