I had this problem with windows 8/8.1 as well but don't remember what I did to fix it and can't seem to figure it out this time. I had to reinstall Windows 10 after upgrading to it, and forgot to write down my settings for this.

I have a simple batch file that I want to run after the computer is idle for 15 minutes. I also want it so that if it runs, then the computer is used and becomes idle again, it runs again after another 15 minutes of idle. However, it seems like no matter what I do, it always runs after only 4 to 5 minutes of idle time. Any ideas as to how I can get it to be what I want?

General tab:
User to run as is my own user account (that's always logged in)
Run only when logged in
Run with highest privileges
Configure for Windows 10

Only trigger I have is "on idle", with only ENABLED being checked.
Only action I have is "start a program", which is the batch file.

Conditions tab:
Start only if idle after for: 15 minutes.
Wait for idle: Do not wait (but doesn't matter what I set it to as it makes no change)
Stop if computer ceases to be idle = checked
Restart if idle state resumes = not checked
Start only on AC power = checked
Stop if switched to battery power = checked
Wake computer to run task = not checked
Start only if network connection available = not checked

Settings tab:
Allow task to be run on demand = checked
Run ASAP after scheduled start is missed = not checked
If task fails, restart every = not checked
Stop task if it runs longer than 1 hour
If task does not stop when requested, force it = checked
If task is not scheduled to run again, delete it = not checked
If already running, stop existing instance