I wonder what is better for performance and “longevity” for iMac: should it be turned off through “Shut down” or should I put it on “Sleep”? I am talking about every single night.
I always put my Mac to ‘sleep’ unless I am going away for longer than a day.
Your Mac can do stuff like Time Machine back ups and other maintenance stuff while in sleep too - Apple call it ‘power nap’ (tho you can turn it off via System prefs > battery).
I’m not sure whether either effect performance much, though Apple used to recommend letting your battery discharge fully once a month and leaving it for a few hours before recharging it - macOS does a lot of this automatically now:
How battery health management helps
The battery health management feature in macOS 10.15.5 is designed to improve your battery’s lifespan by reducing the rate at which it ages chemically. The feature does this by monitoring your battery’s temperature history and charging patterns.
Based on the measurements it collects, battery health management may reduce your battery’s maximum charge when in this mode. This happens as needed to ensure that your battery charges to a level that’s optimised for your usage – reducing wear on the battery and slowing its chemical ageing.
While battery health management benefits your battery’s long-term lifespan, it can also reduce the amount of time your Mac runs on one battery charge when capacity limits are applied. If your priority is making your Mac notebook last as long as possible before recharging, you can turn the feature off.
When battery health management is turned on, your battery’s maximum charging capacity might be limited. Although the feature is designed to improve your battery’s lifespan, the limited maximum capacity might update your battery status menu to indicate a need for service.