Perhaps the point which is the easist to implement is:
"Unlike the transporter, magic items don't seem to break or stop working very often."
This strikes me as the best place to address this! No item should be 100% reliable. There should be cavets to their use, costs and unforseen consequences. How many magic items in folklore were bug-free or 100% safe? Go to Comment
I view messing with time measurements a somewhat low-reward activity - you may add flavor, but you put a new layer of translation between how we are used to reckoning time, and the game world. Worse still since the game rules themselves, unless you are using a home-brew, will also use real-world time.
I see Dates as much more flexible on that front, but messing around with hours or smaller strikes me as somewhat masochistic. I'd need a really good reason for that :)