A blog post – https://cloudblogs.microsoft.com/windowsserver/2018/03/29/windows-server-semi-annual-channel-update/ – has clarified Windows server futures.
Going forward the Semi-Annual Channel (SAC) releases – Server 1803 is due very soon – will concentrate on containers (applications and hosts) and fast innovation application scenarios. Releases will be every 6 months with an 18 month lifetime.
The Long Term Servicing Channel (LTSC) is for general purpose file servers, ‘traditional’ applications (whatever that means), infrastructure roles, software defined datacenter and Hyper-converged infrastructure. Releases will be every 2-3 years with the standard 5+5 lifecycle.
SAC will be Server Core only. if you want a GUI you need LSTC.
Innovations from SAC releases that occur between LSTC releases will be rolled into the next LSTC.
This clarification is useful and the differences between SAC and LSTC now make sense.
I’d recommend that you only use the SAC releases if you need them as they do introduce more churn into the environment given their short lifecycle. I wouldn’t ignore them –keep any eye on the releases as they become available as there might be a feature that makes your life much easier.