I never worry to much about over training the calve muscle. Add some tempo into the raise or some isometric holds. I do 3 counts for the stretch and 5 count for the contractions then you can feel the soreness the next day.
^^^ calves and abs are 2 muscles that naturally can be overtrained
BUT calves are also a very genetic dominant muscle. i am blessed with great calves, but other guys (usually lanky guys) have shit calves and no matter what they do they will always have chicken legs. doesn't mean you can't improve them though
[FONT="]The calf is composed of two different muscles: the gastrocnemius and the soleus, which lies underneath the gastrocnemius, giving the depth to your calf. When you are doing standing calf raises you are working the gastrocnemius. When you are seated raises you are working the soleus.
You need to do BOTH exercises to effectively train the calves. [/FONT]