Twice a week for me, more stable test levels, and lower overall E2. I personally use a 29g 1/2" slin pin. You get no lost medication in the tip, and very little scare tissue. 1/2" is fine if you have somewhere lean to shoot, or you can go SQ with no issues. Drawing takes a minute but it isn't bad because the quantity is so little, and you can warm your bottle first if needed. I do 160mg/week so .4cc twice weekly. This keeps me in the 800-900 range.
If you have any issues then once weekly does work fine, but once every two weeks is too infrequent.
I don't know if anyone can find it, but there is a test cyp graph that shows the halflife drop off is NOT linear.