You can reclaim ships and ship costumes bought through the C-Store on any character on your account as many times as you want as long as you don't already have one claimed on that character at the time.
planning on buying the new heavy escort, but i need to discharge a ship. i know i could just buy the extra two slots, but i'm not using a bunch of my other ships so i don't feel the need too.
however, most of my ships are c-store refits or have the costumes.
before i discharge one i want to make sure i won't have to spend cpoints to get the ship/costume again.
side question, if i make a new character, do i have access to the cstore ships/costumes on that one as well?
As to discharging ships, the purchase of a ship is a permanent unlock for your account. That means that it is available to any eligible character (e.g., rank and faction) and you can claim it as often as you want, so you can have it on more than one character and you can claim it, discharge it, then claim it again on the same character. The only caveat is that they will generally be treated as unique items, so a single character can usually only have one active at a time. Thus, you could have a Tac Odyssey and a Sci Odyessey (two different ships) on one character, but not two Tac or two Sci Odysses (same ship) on the same character. Two of the same ship on different characters, yes. The same character, no.
As for how other items in the C-Store go, check the "fine print." The item in the C-Store will generally have disclaimers like the following:
Ship Costume ("Comet Class" in this example): "A variant of the Luna class, purchase of this option unlocks the Comet Class ship parts for your Rear Admiral rank Federation characters."
Bridges ("Defiant" in this example): "Note: Purchase of this option unlocks these bridges for all Federation characters on an account. These bridges can be used with any Federation Starship. "
Ship/BOff slots (Ship in this example): "Note: Purchase of this option adds two (2) ship slots to one (1) character."
Pet (Exocomp in this example): "Note: Purchase of this option is a single item unlock. If you discard, sell, trade, or auction an Exocomp Companion you WILL NOT be able to claim a free replacement from the C-Store. Once the item is unpacked from your inventory it will be bound to you."
Not all items in the C-Store carry such a disclaimer. For instance, consumables like Master Keys and Duty Officer packs, especially tradable consumables like those, don't carry a disclaimer, but then it is not reasonable to assume you are buying a perpetual supply of those kinds of items, so the default assumption is that this is a one time purchase for a single character. Ships are assumed to be a permanent, account-wide unlock, so sometimes you see a statment confirming that and sometimes you don't.
So to summarize your concerns, yes, you should be able to discharge a C-Store ship and, if you want it back at a later date, you can reclaim it from the C-Store for free. You can also claim it on other eligible characters on your account since it is a permanent, account-wide unlock. Ship costumes you purchased from the C-Store will also be available to eligible characters on your account. Those are both true, of course, unless you see a disclaimer stating otherwise, but in both those cases, I don't think there are any exceptions presently.