My conceal permit is going to expire soon, and I am aware that NH has constitutional carry which is great. But being I am currently stationed in NC and heading to CA (which i also am aware CA doesnt recognize the permit) but the NH permit at least allows me to carry in a few other states. That being said my question is Ill be taking leave this week to come home for some admin stuff, am I able to apply for my permit and have it mailed to me or is it always just pick up in person?

Probably the best thing would be to call your local department, explain your situation, and ask them. 

Tried that once myself, they made me pick it up. Wouldn't even let my father who is a state trooper pick it up for me.