Most reports claims Closing app help to save battery as it stops apps from running in background and helps run the device smoothly and faster as less ram is being used. So it is recommended to close apps and also to restart device in regular basis for device best performance.
If you've found my post to be helpful, please like the post. If my response resolved your issue, please press the "✓ Accept as Solution" button.
On the other hand, OneUI incorporates adaptive battery management that can close unused apps for you and drastically reduced the impact of those that are running. I've also seen articles suggesting that modern smart phones, unlike computers, don't actually keep apps running in the background, but rather keep the recent apps as shortcuts to get back in more quickly, and that closing apps then later launching them from cold can actually cause a resource drain. In other words, I think you ask a good question, and that the answer is not necessarily clear.
I rarely close apps on my S9, and don't run into issues unless a specific app misbehaves by failing to throttle down.
Hey @Samsung_RvXgVYO, I hope you're doing well.
Although it isn't exactly necessary to close all app all the time, it is recommended that you do regularly close un-needed apps and optimize your device via the Device Care app.
The Galaxy S8 is still a great phone and can get a full days use if optimized correctly.
If you need further information on this matter or any other related to your Samsung devices, please do not hesitate to let me know.
It it's better to keep apps open. Allow the system manage RAM (random access memory).
Closing apps slow the phone down as it will need to load the app from scratch, taking more battery with it.
So there you have your answer(s). In years past, I think it was necessary to close apps just like I do on my Windows PC. I'm no longer convinced of that, but others are. It probably depends on the device, installed apps, and actual usage. I think your best bet is to test it for yourself, but very deliberately. In a given day, decide if it's gong to be a "close the apps" day or a "leave then running" day and see how it affects your performance and battery. Sorry it's not clear.