Hi,
If your talking about the phontinia red robin, ive just given both the hedge in front of our pool approx 20 feet long and the hedge near our gates approx 8 foot of red -robin and that was yesterday,
they grow all summer and i'll give another tidy up prune about september so ive not got to much growth for the winter snow to land on.

I try to keep the hedge by the driveway 6 feet high and the one by the pool about 5 feet high.
Hope this helps.

If its hedging, Dungy's advice is good (except, if you're somewhere cold like up north, do the second cut in early August or leave it till mid to late October), if you're growing a single specimen and don't want it to get treelike, now is a good time to cut it right back and reshape.