Since the Creation Kit came out, some contributors to the UESP Skyrim Wiki website have put together
an article on containers and
a page on safe locations. Apparently the Creation Kit allows you to look at the coding of containers and locations to determine whether a container is "safe," i.e. that it will not respawn its contents. The following are some general observations from reading the article:
1. There are certain types of containers that are not coded to respawn regardless of location. These include coffins, cupboards, dressers, end tables, strongboxes, and wardrobes. Containers confirmed to have respawn coding in them include apothecary's satchels, barrels, chests, sacks and satchels.
2. There are certain locations that are in the game that are non-respawning locations. This overrides respawn coding in any containers at the location so any container in a safe location is safe for long-term storage.
Sky Haven Temple is not listed on the safe locations page and while I don't know if the page is comprehensive or still a work in progress the safe bet would be to assume that the contributors looked at all the obvious places that a player might want to use for long term storage of items which would have included Sky Haven Temple.
One additional note, respawn timers will reset whenever you enter their cell (a defined area surrounding them, usually the entire zone) so if a chest doesn't reset for months it doesn't mean it's safe in the sense that it wont ever respawn. It just means that you are revisiting the cell often enough to reset the timer. As a practical matter that may make it safe for the player. e.g. if the timer is over 10 days and the player always enters the cell on at least a weekly basis, but if for whatever reason the player is away longer, the items will be lost when the container respawns its contents.
