Then you must have had a defective or damaged battery or apps running that put a heavy strain on the battery because it should have had substantially more than 6 hours SOT with a 4800 mAh battery. My Note9 has only a 4000 mAh battery and I get over 6 hours SOT at max brightness streaming HD content. The S21+ probably should get at least 7 or 8 SOT, perhaps even longer.

Try charging your phone to 100% (not something you should do regularly), then use your phone as you normally do and run the battery until the phone shuts off (also something you shouldn’t normally do). This should recalibrate your battery to show a closer approximation to actual battery percentage. After you do this, check in Device Care, Battery, Since Last Full Charge to see what your actual SOT was. I can get around 6 1/2 hours on my Note9 on max brightness, so I imagine you should be getting significantly more than that unless there’s a defect causing the battery to degrade faster than normal. If not, you should probably just get a replacement phone or battery. Hope this helps.

Look at your battery usage and see how much any recently installed apps may be draining your battery. I have a Note9 and for some reason, X (Twitter) seems to make my phone run warmer than usual and uses a lot of battery. Also, some of the newer ChatGPT apps seem to drain battery even though all the AI is done in the cloud.

That extra 2GB could make the difference between an app in the background staying in memory or having to be reloaded when you need it or a little extra performance in a game you really enjoy. It’s only $50 extra that you won’t even miss down the road. I say go for it.