Well, you can find all the gory details here:
http://wesworld.jk-clan.de/thread.php?threadid=153&boardid=4
But the basics are, you need to do a refit (cost = 1/4 of light displacement) after 15 years' service, and a rebuild (1/2 lt.disp.) after 30 years. There are no "yearly maintance" costs (that's something we'll need for WesWorld2...).
If you don't do the refit, you have a "5% penalty to its combat performance" (whatever that means, since we have no combat rules yet) per year that the refit is "overdue". Skip a rebuild, and you get a "5% penalty to all aspects of her operation (combat, speed, damage control, etc) as parts simply wear out".
There's also a "reconstruction" option (cost = 3/4 lt.disp.) for carrier conversions, etc.
My suggestions re: "mothball rules" stem from the concerns, started by Hooman (and which I partially share) that some fleets might be "too big for their britches", i.e. too many ships and not enough men. Mothball rules would allow you to "stash" these ships, for reactivation in event of war, instead of scrapping them.
In addition, this would allow you to "reserve" ships in need of repair, or refits/rebuilds, until you had the "funds" to repair/refit them, without having them sitting around rotting.
Basically, here's how I see "mothball rules", the latest version:
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2.5 Mothballing ("Ordinary")
Ships may be "mothballed" ("placed in ordinary") at a player's discretion.
Placing a ship in mothballs costs nothing. While in mothballs, the ship "decays" at a rate 1/2 of that which it would wear if it were in service.
To retreive a ship from mothballs, the following must be performed:
If the ship is due for a rebuild, it must be rebuilt before returning to service, using the rebuild rules (2.2.3) (i.e., putting a ship in mothballs is not a way around rebuilding it).
If the ship is not due for a rebuild, it must be refit using the refit rules (2.2.2), regardless of how long the ship has been in mothballs.
Ships requiring repair do not "repair themselves" while in mothballs.
Note: Ships in mothballs do count against any and all of a country's treaty restrictions.
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Folks, I'd appreciate additional input on this...