I think your post answers your own question. Most of your post is indicating the financial aspects of ownership have you concerned. Frankly, to me it looks like a list of the reasons you think it's time to move on, maybe to streaming??
There will always be trade-offs in dealing with content, and content delivery services. By now, most of us enthusiasts know the difference in the different services (Apple TV, Netflix, VUDU, etc,) and Kaleidescape, so I won't list the positives and negatives of each.
I think by now most of us have already done the cost/benefit analysis in evaluating whether to remain in the K ecosystem or move to a different service. Most decided to stay, and in doing so either added a Strato to their Premiere system, or moved to Encore completely (upgrading their Premiere components, or selling), or decided to keep their Premiere systems, and may or may not have added a streaming service as well.
All Premiere owners face the same difficult questions:
HOW LONG WILL I BE ABLE TO MAINTAIN MY SYSTEM? The answer has a few considerations. The components in the system are clearly a factor. The 5U server was discontinued long ago, it has no real value except as a trade up component, or perhaps for someone that has a 5U and wants a backup 5U. There are no replacement drives available for the 5U
Similarly the 3U is on its way out, it is no longer sold or supported by K (with exception to a few that remain under warranty). The only functionally important repair part available for the 3U from K is the power supply kit (with fans) at a cost of $860 retail (price increase recently). 6TB drives are still available, but given what happened with the 5U drives, I assume not forever. The standard 1U is also no longer sold, and out-of-warranty units are no longer supported. Drives are the same as 3U.
The only Premiere server still being sold by Kaleidescape is the 1U+, so that server should be serviceable while under warranty. It also offers a model with 10TB drives. Older Premiere servers can be replicated to the 1U+ (subject to available storage).
K is still selling the M300 Player, M500 Player, and the Vaults, so some Premiere components are still. K does also offer an out-of-warranty replacement service for some Premiere components, subject to availability (basically older equipment returned from upgrades, or exchanges, is "remanufactured" and made available for the OOW exchange service (prices vary).
The other consideration is how much money are you willing to spend to maintain the system? Obviously, personal finances come into play here, but I think to a large extent this is also driven by a desire to maintain the "collection," as discussed in my next comment.
The 2nd difficult question for Premiere owners is:
WHAT DO I DO WITH MY COLLECTION IF I MOVE TO ENCORE (or if concerned about Premiere longevity).
To some extent the answer is dictated by the size of your collection. The larger the collection, the more disappointed you will likely be, because it's less likely that all of your titles will be available in the Store, and those that are, and not UV/DD, will cost you money to put into an Encore component.
You can of course hedge a little in keeping Premiere by perhaps moving to a 1U+ server, and upgrading older players to gain a longer warranty.
All of that said, the other option is to do what many of us have done, add Strato and Co-Star, work with both systems, do what you can to maintain your Premiere system for as long as possible, while at the same time slowly adding some of your more important movies to Encore using Digital Offers, etc..
All of these options involve money, no way around that, but given what you own, you already know that, so it comes back to my original comment about cost/benefit, and only you can really decide that aspect when evaluating options.
Jim
(Note: Much of what I wrote above is to help educate others, not necessarily you, I know you already understand these issues.)