Custom ROMs don't always match the stability of the software you get out of the box. Sometimes, though, they manage to surpass it. Either way, CyanogenMod will typically support a device for much longer than the company that made it. It's a great way to breathe life into hardware that shouldn't have to die just because its manufacturer decides to move on.
The Galaxy Tab S 10.5 and 8.4 are two of the top Android tablets to come out in the past few years. In the summer of 2014, Cameron called them the best options you could buy at the time.
There are Wi-Fi and LTE variants of each, and support has to roll out for each model individually. We saw the Galaxy Tab S 8.4 Wi-Fi get CyanogenMod support back in March. Now the LTE version, codenamed klimtlte, is getting its turn. So is the Wi-Fi variant of the larger Galaxy Tab S 10.5, also known as chagallwifi.
You can find the nightly builds at the links below. Note, while nightlies tend to be usable enough, these may not be fully ready for primetime. Proceed with care.