In the Open source software development model there are long term stable versions available. For example Firefox ESR, Debian stable, Ubuntu LTS and Linux kernel LTS. What most users doesn't know is what the difference is to the normal version. In most cases, the long term version is older which means, it is not the latest update but its outdated. If the aim is to update the system to the latest sourcecode, LTS versions doesn't make much sense. On the other hand, Firefox ESR and Linux LTS are available as an option so why are LTS versions are available if they are a poor choice?
To understand the situation we have to take a look into closed source software development. All the commercial software is published in long term version. The Windows XP Operating system is available only in the LTS version, the same is true for Windows 10, Mac OS X and so on. The most obvious difference between a rolling release and a long term release version is, that in the LTS version some components are missing. That means, the Firefox ESR browser is a feature reduced version of the latest Firefox browser. If the normal Firefox software has a menu with 10 menupoints, the ESR version is equipped only with 8.
The decision pro or against a LTS version has to do with the missing features. Its the difference between 8 menupoints and 10 menupoints. From the development perspective the interesting question is, why are the missing 2 menupoints not available in the LTS version? It has to do with stability. Improving a software with additional features needs a lot of work. If the manpower in terms of programmers is small, it will take some time until the missing 2 menupoints are added.
All long term versions have in common that with a time delay all the missing features are added. If the endusers waits a bit, the imaginary Firefox ESR version will have 10 menupoints too. The only question is how long does it take. In most projects, the time gap is 1-2 years. That means, the developers have programmed all the 10 menupoints already, but they are only available in the trunk branch but not in the production version. If a software contains of a long term version plus a trunk version at the same time it's a positive situation. It means, that the development team is improving the software and another team is testing the changes for stability and security. On the other hand, if a software project contains only of a trunk branch and doesn't offer a LTS version it's a toy project. That means, the software is programmed just for fun but isn't used in reality.
Let us analyze this hypothesis in detail. Suppose a development team is trying to improve the security, the stability and the amount of features in a software. The only way in doing so is by creating additional branches. One feature branch, one security branch, one stable branch and so on. After these branches are created a time lag is the result. That means, the security team will analyze version 1 of the software, but the feature team is implementing version 2 of the software. The security team is testing something different from the development team.
Let us imagine, the software project contains of a single branch which is called trunk. It is not possible to establiish a quality control on a single branch development model. The reason is, that all the latest updates are commited into the trunk branch and it makes no sense to ask if a certain version is secure. Because the version is changing twice a day. The result is, that a trunk-only repository isn't tested for stability nor security. Instead it's the development version which isn't recommneded for productive usage.
Let us investigate why some software projects have no long term version. The reason is, that the software developers want to minimize their effort. Its a one man team or a two man team which is programming the sourcecode. No quality control is available. Such a software development cycle isn't used for commercial software. Because most customer are paying money for the software and in return they are expecting a high quality. Only open source developers are bold enough to publish the trunk version of the software.
Point releases
Software development consists of two conflicting roles. The end user of a software likes to install the program on the PC, needs a documentation, and is interested in a bug free system. The needs of the software developers are the opposite. A software developer likes to modify the code twice a day, he is testing out new modules and he doesn't like to waste his time in writing a documentation.
Two conflicting roles means, that if the end user is happy, the developer isn't and vice versa. It's only possible that one social role in the game wins. The reason why long term versions were invented is to fulfill both needs at the same time. Let us first describe the end users perspective. The end users is downloading the LTS version of the software. This version is bug free, is well documented and runs out of the box.
From the developer perspective the LTS version is useless. The developer has no need for a documenttation because he has written the sourcecode himself, and he has no need that the software can be installed easily, because he compiles the sourcecode from scratch. What the developer is prefering is a trunk branch in which new commits can be applied. Because of the different needs, there are two versions of the same software available. The LTS version which is adressed to the enduser, and the trunk version which is the playground for the developers. Between both versions, there is a time lag. That means, they are out of sync. This allows that both social roles are happy at the same time.