The TKR-750 is scheduled to be "end of life'd" in September of 2017. Kenwood shows the NXR-710K as it's suggested replacement. That doesn't mean that support for the TKR-750 will vaporize, it just means that getting parts, software updates will grow more and more difficult. Also, knowledge will eventually erode and the trained/experienced people rotate out.
Decent repeater if the entire system is set up properly. We're using a TKR-850 at one of our sites, but it's turned down to 5 watts.
Using analog encryption will pass right trough these repeaters, that's not an issue.
I'd consider looking well into the future for your designs. While a simple analog repeater may work fine right now, be looking 10 years or more into the future of any of your designs. Not sure how long you plan on running this system, some will push their system until it fails then replace. Some agencies will have a depreciation scheme with a planned replacement date on the horizon. Depends on what you need. I usually try to plan out 10 years and figure on replacing at that point, especially for anything public safety related. Waiting for it to fail, then trying to secure funding, etc. can be a hard way to do this.
I'd look at one of the newer repeaters that can handle analog now and P25 or other digital mode later on with a software/firmware/licensing upgrade. While it may cost fractionally more now, that will probably cover you well out for 10 years at least.
In other words, I'd personally be hesitant to invest in analog only gear at this point, especially something that has an expected life span of 10 years or more. It might save you money today, but it's likely that in the long run it's going to cost a lot more.