mjhjmtu

I'm new to Arch Linux and I want to ask how often will I need to reinstall whole Arch Linux.

So if you're also a Windows user you'll (or you might) now you'll need to remove and reinstall a new windows to reduce the disk usage or for some security reason (like viruses etc.)

So I'm wondering how often will you need to do the same process for Arch Linux (or other Linux distro)?

No stable operating system requires reinstallation as a matter of general use.

I can think of a few reasons one might want to do so, and why they don't apply to a typical Linux distribution:

1. 
   

   Installed application programs acting erratically.

   
   
   

   If you keep track of applications through the package manager (pacman in the case of Arch), you can reinstall only the misbehaving application. Though if you bypass the package manager, you might be asking for trouble.

   
   


2. 
   

   Disk layout of system files.

   
   
   

   Over time, updates happen. This could result in system files being placed randomly across the hard drive, rather than in a single (fast) place. This could be the cause for system slowdown. Many (but not all) Linux installations separate the system files from the user files by partitions, which lessens the impact of this (among other benefits).

   
   

Now, if you find your system in a broken state, it may be easier to reinstall from scratch. This should be a rare state though.

There is no case where you need to reinstall any linux unless it's hacked and security is compromised, keep in mind this only apply to server machines where security is very important. Sometimes it's just faster and easier to reinstall Linux instead of reviving broken system. The need of reinstalling is purely based on your Linux skills how often you break your system, by pasting commands that you don't know the meaning of. You can have linux and Windows on same machine you won't get linux infected with viruses from your windows. I didn't reinstall my arch for 4 years, using it daily.

I'll ask the counter question - how often did you reinstall Windows? Windows - a fairly stable system, if with it (as with any other OS) properly handled. I still have Windows XP installed on one of my computers (since 2010) without antivirus, firewall and other add-ons. Yes, not on one - on the second multi-boot with Windows XP, Windows 7 and Xubuntu. There is no antivirus on any windows. And this despite the fact that all work and interests on the Internet (including pornsites sometimes;)). So what? 5-6 years at least. Linux I use from 2011-2012 - on all 3 computers installed Xubuntu as the main system.
The last installation after buying another laptop:

$ sudo tune2fs -l /dev/sda1 | grep create
Filesystem created: Wed Oct 19 21:29:42 2015

Everything depends not on the system, but on the person. Accuracy, care and the creation of backups - this is the guarantee of longevity of the operating system. Linux can be spoiled by one careless command

$ sudo rm -Rf --no-preserve-root /

Always think what you are doing, ask, if you do not understand, look for information on the right questions - and your life will be long and happy