Maybe we're just thinking about different phases of the game. Throughout most of my games I'm only in one or two select wars, but in the end everyone comes after you and you do get more rapid fleet action. By then, though, your economy is probably rolling well enough to make it easy to ignore a few blockaded ports or absorb the cost of ship upkeep.

So I'd say until you get to ~35 provinces you really don't need a standing navy, and after that you can probably afford it. A lot of the rare early blockades I catch are 'AI Council mission' type deals too, where they'll sign an immediate ceasefire and pay you for the privelege if you have a diplomat near them.