WLMS is the service that gets installed when you use an evaluation key That's what checks for the license change and performs the reboots, and removing it will indeed stop the OS from rebooting.
I don't know if there are any other checks though that might switch the OS to non-genuine at some point, so I just did a reinstall using a non-eval key to be safe.
Windows Embedded Standard 7 Runtime (x86) - DVD (English)
产品密钥:MPMVY-PP762-WWVBC-83RXJ-2H7RH 静态激活密钥
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Windows Embedded Standard 7 Runtime (x64) - DVD (English)
产品密钥:MPMVY-PP762-WWVBC-83RXJ-2H7RH 静态激活密钥
*************************************************************
Windows Embedded Standard 7 Toolkit (x86) - DVD (English)
产品密钥:7XT84-3XQFP-YMXQF-PP96H-F74DV 静态激活密钥