Navy

[Sheogorath]

I generally avoid having a navy at all. Ships are expensive and you go through them fast. And their upkeep is ungodly.
If I HAVE to I purpose-build fleets then get rid of them quickly to avoid that horrible upkeep. Its not the most effecient method, but I prefer to focus on my land based forces anyway.

[DVX BELLORVM]

If I HAVE to I purpose-build fleets then get rid of them quickly to avoid that horrible upkeep.

Considering their cost/upkeep ratio, that does sound like a good compromise.

[Ramses II CP]

Yeah, if you're keeping a stack of ships around it had better be small and blockading an enemy port, otherwise it's like bleeding florins. I tend to use the mercenary ones for transport only until it's time to go to the new world.

[Cheetah]

Don't know. The upkeep is not terribly high compared to elite units such as knights etc. Also it is not terribly high compared to the income loss due to enemy blocades. Also, the more factions you are fighting the higher the chance that one of them sends a fleet to blocade your key port.
So even though I am not too eager to build large fleets, I find myself, sooner or later, depending how many ports I have and what at sees, to be forced to build at least a half stack or full stack of ships. Since the AI usually cannot focus its fleets one stack (half stack) is enough to wipe out any competition.
Also if you want to transfer troops with ships you need a decent stack, as tranfering troops with merchant gallleys is a suicide in the later game (assuming you are in fight with a decent number of factions).

[Ramses II CP]

Hrm, I haven't had that experience. Sure I get a port blockaded every so often, but then I just build some ships and beat the attack back. My armies aboard ship are almost never intercepted and even if they are the AI doesn't sink all the ships (So I don't lose troops), and after the 'retreat' I'm usually closer to my intended target than they are.

The key difference between high end troops and ships is that you can sack something with those high upkeep soldiers. With the fleet you can, a few times a game when the AI is feeling chippy, maybe protect a port or blockade an enemy one and slightly reduce your upkeep expenses. 90% of the time, however, they're useless florin bleeds and their upkeep costs make it so it's cheaper to recruit a new fleet every 4 turns, as needed, instead of keep one hanging around that long.

[Cheetah]

Maybe I am just in war with too many factions at the same time. I am almost always get blocaded by someone. Also, once I lose a naval batttle the enemy fleets play pinball with mine passing my depleated fleet from one enemy fleet to the other till it is sunk.

[Zim]

Like Cheetah, I sometimes have trouble with enemy navies, especially at that point at which the entire world attacks you no matter how peaceful/bevenolent you are.

I find keeping ships on hand sometimes actually deters enemies from blockading in the first place.