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If I run PC 9-10 Hours Daily ,will any problem occur?Because of slow download Speed I have to do it.What is the standard time limit of running a PC?
I think it really depends more on the usage of the computer. Heavy usage which could cause components to heat up and cool down is going to be a big factor in hardware failure. The second would be the environment, and how much dust/debris is your computer going to be inhaling? If it is very dusty, things will start the get hotter than they should and problems could start occurring. However, these are side effects of running the computer so a computer in perfect conditions could run for a very long time without any issue.
Outside of the technical areas, consider that most companies(mine included) allow their desktop computers to run 24 hours a day, and are only rebooted when necessary. Servers run even longer, typically going weeks if not months(or even years) before they are shutdown or rebooted. At home, all of my laptops and desktops run all day, every day.
There really is no time limit on how long you can run your PC. If your fine paying the meager electricity it uses during operations, I'd just let it run all the time.
While my own experience isn't empirical data, I have several desktop computers that have been powered on and "doing" things like remaining connected to the company VPN and running RDP sessions for days at a time. Sometimes the computers are connected to the VPN for weeks. I have not observed any problems with the systems that I can attribute to the computers being powered on and active. I do need to take the computers down every couple of months and clean the dust from them, however.
If you do leave the computer on your biggest concerns (in no particular order) are likely: power consumption, dust accumulation, lights, noise, and heat (both damage to the system if it stays dusty and waste heat).
There are two main issues to consider:
Let's leave aside the electrical costs (both directly involved in running the PC and ancillary costs like air conditioning to compensate for the heat generated). Computers today are fairly energy efficient and for a single computer, the impact on your electric bill is nil.
Hardware wear & tear
The greatest stress that happens to a computer system is cycling the power on and off. I used to manage an IT department that was responsible for 2500 computers. Whenever we had a power outage, whether planned or unplanned, we lost several hard drives and other components (e.g., power supplies and motherboards). In terms of overall percentages it was fairly low (<1%), but the critical point at which failure occurred was in powering the machines off & on. Our policy was to leave all machines running all the time. It's what I do with my machines at home, too.
Operating system stamina
Every OS has issues with memory leaks and other "stuff" that accumulates in memory and impacts its effectiveness & performance over time. The more stuff you run, the more likely you are to see a performance impact by not rebooting your computer. Every person's mileage varies, but I think it's good practice to reboot at least once a week to clean out the accumulated "clutter". Some people reboot more often, while others go for a month or more before rebooting.
Note that "reboot" does NOT mean powering off and on the computer - for that, see above. Reboot is a software only operation (e.g., under Windows it is called "Restart"
Bottom line - never turn it off - reboot as needed.