Launchd process behavior just wanted to ask a quick question I can't seem to find a straight answer to.  What is normal "launchd" process behavior I should be seeing in Activity Monitor?  Right now it is writing GB's of data daily, I usually just browse the internet and stream videos. Feels like my HDD is constantly spinning up and down and when I watch disk activity the only thing that consistently goes up is the launchd process, which from what I understand is basically the OS.  So is this normal or do I need a fresh reinstall of High Sierra?  

As far as system performance this isn't aversely affecting anything, I am just worried it will wear out my HDD faster than usual.  I am on a Macbook Pro Early 2011 13" with a third party battery from OWC (about 2 years old) and 16GB of RAM from OWC (just installed within the last month).
Something definitely doesn't sound right with what you're describing. Most descriptions of Launchd describe it is mostly doing nothing as described in this article titled: What Is launchd, and Why Is It Running on My Mac?:


  It’s very rare for launchd to take up many system resources, and when
  it does happen, rebooting your Mac is usually enough to fix it.
  Occasionally a buggy program trying to launch faulty daemons can cause
  launchd to use up a bunch of CPU. If you’ve installed something
  recently, try removing that and seeing if it helps.


You can check on what it's doing with this command:

$ launchctl list | head
PID Status  Label
-   0   com.apple.SafariHistoryServiceAgent
-   0   com.shazam.mac.ShazamHelper
-   0   com.macpaw.CleanMyMac4.HealthMonitor
36706   0   keybase.updater
702 0   com.apple.Finder
1256    0   com.apple.SafeEjectGPUAgent
64713   0   com.apple.quicklook
-   0   com.apple.parentalcontrols.check
-   0   com.apple.PackageKit.InstallStatus


From the sound of it with the logs being written to it sounds like Launchd is logging debug level on either one or more processes on your system. You can read more about changing the log level here:


How do I activate launchd logging on OS X?



There's also this aSE Q&amp;A titled: New stats file created every 20 seconds in /var/log/com.apple.launchd.peruser.94? which doesn't have an answer but does describe and show another issue related to Launchd where it is excessively logging files.