Most likely explanation is the high number of employees on sick leave, not just at Amazon, but basically everywhere.
Seeing the erratic delivery pattern for a range of items. As long as the product in question is in stock, it's not a supply shortage, but more likely a lack of warehouse/delivery personnel.
Pros of leaving a system on 24/7 is the lack of thermal cycling. Every time a system boots the components heat up, with different (internal) parts heating up at different rates (due to dissimilar materials). This puts a fair bit of stress on components and is one of the factors in component failure (along with electron migration).
Whether this is a concern mostly depends on how long you wish to keep using the components for. If you'll build a new PC and trash this one in a few years, it won't matter, and you can save energy & money by turning it off when not in use. If the goal is to keep using the parts (especially CPU, mainboard, etc.) for many years (passing/selling on), then leaving the system on 24/7 can help with that.
hackkitten got a reaction from An0maly_76 in Is there possibly a power supply unit shortage?
hackkitten got a reaction from Jorgemeister in Is it alright to have my system running 24/7?
