There's no hard-and-fast rule against signing a key out long-term to anyone, provided it isn't a key that unlocks external doors (and obviously they won't sign out a key that opens the cash reserve drawer, either). At my store there were several TLs who had their own keys to the fixture room/clerical (same core). It's all up to the STL's discretion, since losing one of those keys would not require a complete re-keying of the store. The pin lock uses, if I recall correctly, a core used for nothing else at the store--so if your store's management trusts you not to use the key to steal trailers at night, there's no reason why they can't give you one.