I'm crart training my cairn pup (5 months old) but he still urinates in the crate while I'm at work. At what age does he gain long term control?

There's not really a set age. Some dogs just take longer to adjust. Have you made sure that the crate just isn't too big for him? If it's too big, he can urinate in one spot and will still move around so as not to lie in it. Also, if there is any kind of soft bedding, like a blanket, in his crate, it may soak up the mess so he's not really "disturbed" by it. Try taking everything out--sometimes that helps.