The Samsung Galaxy S8 and S8+ have been moved to a quarterly security update schedule after three years receiving monthly security updates.
These phones have now reached their third birthday and it was expected for them to move to a quarterly schedule.
Samsung software updates

Up until 2019, Samsung only supported their flagship phones for three years. These three years would include two major OS upgrades as well as monthly security updates. Afterwards, however, support would stop completely, leaving users of the obsolete phone at risk of bugs and security issues.
With the S7 and S7 edge, however, Samsung did something different. Come these phones’ third birthday, Samsung did not end support. They instead demoted these devices to a quarterly schedule, meaning they get updates every three months. This continued until last month, where Samsung ended support fully for these old devices. However, this gave Samsung users hope of more software support, and maybe one day, a third OS upgrade for a flagship.
S8 demoted to quarterly updates

Yesterday, Samsung demoted the Galaxy S8 and S8+ to quarterly security updates.
This can be good and bad. It’s good in the sense that it’s better than ending support completely, and also gives S8 users time to upgrade to a new phone. But it’s bad in the sense that crucial updates will only come three months which a severe security flaw could be found in between the last update and the next. Monthly updates eliminate this risk. However, quarterly updates will still patch up bugs from previous months, so hopefully the S8 and S8+ will remain quite secure.
OneUI

In early 2019 the Galaxy S8 and S8+ were the oldest devices to get OneUI 1, which revamped the system UI. This year, S8 users hoped for OneUI 2 to come, but sadly, it didn’t.
However, the S9 and S9+ are the first devices from Samsung to feature Project Treble, making distributing updates easier. This could mean more software updates in the future. With OneUI 2.1 coming to the Galaxy S9 and S9+ soon, this could give hope for better software support in the future.
Has Samsung solved their software update problem yet?

No, they haven’t. They’ve added an extra year of quarterly updates on to the three years since phone released, but let’s not deny: there’s still issues. Even the newest and most expensive Samsung flagship phones are destined for only two major OS upgrades whilst Apple’s iPhones and even Google’s Pixels are getting more now. Although hopefully Samsung releasing OneUI 2.1 to the Galaxy S9 and S9+ is a small sign of hope, they still have a lot to do if they want to compete with even the Pixel phones, let alone iPhones, when it comes to software updates.
Conclusion

The S8 and S8+ are great phones, there’s no denial there. However, if you own one it may be time to start looking at an upgrade so you don’t end up without updates. It is nice to see Samsung support devices for longer though and hopefully they will start releasing three major OS upgrades considering the Galaxy S9 and S9+ are set to get OneUI 2.1 soon.