Is it okay to keep opened loose leaf tea packages in the freezer?
There's a lot of disagreement on this question online, much of it uninformed.  There are also a lot of assumptions that seem to go along with the question of freezing.

First of all, despite warnings on many tea websites, let's be clear that tea producers and shippers frequently keep tea refrigerated or frozen for long-term storage.  It's true that in those cases, we're talking about vacuum-sealed containers often with nitrogen gas or some other way of lowering moisture.  Moisture is an enemy of loose-leaf tea.  So the question is not whether or not you can store teas in a freezer: obviously, major tea sellers do sometimes.  The question is how to do it properly.

Some would claim it's impossible.  Some reasons:


freezing will harm the cell structure and damage the tea
you'll get too much condensation, which will degrade the tea
you'll get freezer burn from freeze/thaw cycles
odors from the freezer will permeate your tea


The first thing is a bit true, which is why major Asian tea producers (to my knowledge) tend to go with storage around 5C or so.  But the trade-off (as with much frozen food) is that you get the tea to last a lot longer in the freezer than at room temperature or in the fridge.  So yes, keeping tea in the freezer is probably not as good as serving it fresh from the package in the first few weeks or even few months.  But for longer-term storage, the freezer will keep the quality higher than storage at higher temperatures.

As for the other concerns, most of them have to do with poor storage containers and methods, not freezing itself.  You will want to store tea in a container with as much air removed as possible.  So some sort of sealing bag that can conform to the amount of tea is probably better than a rigid container.  On the other hand, you need a completely sealed container to keep odors, etc. out, so if necessary, you might try a sealed bag inside of a more rigid sealed container for an extra layer of protection (if you're not confident in the seal of the bag you're using).  Freezer burn is unique to freezing, but it can be mitigated by the same precautions, as well as storing tea deeper in the freezer where it is not as likely to experience freeze/thaw cycles (as opposed to on the door).

For obvious reasons related to the above, you shouldn't store tea intended for daily use in the freezer.  Pulling the container in and out of the freezer will expose the tea repeatedly to warm, humid air, which will lead to degradation.  Your plan to keep the long-term bulk storage in the freezer, while keeping smaller quantities at higher temperature is good one.

Nevertheless, most sites assume you'll store your tea improperly, in which case freezing is probably not a good option.  But you don't need to go to extremes with commercial packaging to make freezing viable.  Here's a page with some actual experimental data about storing green teas at various temperatures, and they didn't use nitrogen/low oxygen/special low moisture packaging for freezing or anything.  They found freezing green tea was best for long storage, refrigeration was also good but changed the tea a bit, and room temperature tea degraded most over time.  (In several searches, I was unable to find any similar experiment that showed significant problems with freezing, as long as packaging was sufficient.)

Also keep in mind the guidelines listed there (and elsewhere) for warming up frozen tea.  If you pull a container out of the freezer and open it up, moisture will rush in along with the humid air and condense on the tea leaves, which can cause them to degrade.  Instead, it's best to wait a day or so (depending on size of bulk container) for tea to come up to room temperature, then use the tea.  Ideally, it would be best to perhaps store frozen tea in individual packages with the amount you would want to thaw each time.  (Even individual airtight bags inside a larger even more airtight container could work.)  

If you don't want to go to that trouble, you'll have to play off the advantages/disadvantages of how to remove the tea from the bulk container.  If you open it up without letting the whole bulk package thaw, the moist air each time will contribute to problems.  But if you do let it completely thaw, the tea will undergo more freeze/thaw cycles, which will also harm it over time.  If you're relatively quick with removing tea and are sure to get as much air out as possible before returning to the freezer, I'd probably go with the former method (not thawing the whole package), rather than make the tea undergo more temperature fluctuations.

However, with all this in mind, I'd probably start by following the procedure you tend to use with your refrigerated tea that you're currently happy with.

Oh, lastly regarding oxidation: although I couldn't find any good sources on this quickly, my guess is that black teas compared to other teas will be more stable if stored in the freezer, just as they are at room temperature.  With greens, oxidation will be a lot slower in the freezer than at room temperature (or even in the fridge).  As long as you avoid freeze/thaw cycles as much as possible, as well as keep excess air/moisture out, it should allow your tea to stay fresh much longer.