If you have enough room in your safe, your method sounds fine. Having the safe in a climate-controlled area is essential. Be sure to put a dessicant (water absorbing) pack or dehumidifier inside. If the guns are stored this way, I doubt they need to be checked more than once a year.

If you get short on space, using gun socks (Sack-Ups or similar) instead of the boxes takes much less room. One of the more advanced collectors I know uses Sack-Ups and a case, but he must have a lot of room and worry about guns contacting each other.

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Alan
SWCA LM 2023, SWHF 220