Question about campaign/ship respawn.

[Insolent]

I'm wondering if there's any downside to sinking battleships early in the game.
By that i mean, if i sink some (while i'm waiting for march and the next assignment), will it be harder for me to find battleships later if i get a mission to sink one? Basicly the question is, is there a finite number of battleships, or do they respawn?

Thanks in advance.