You have noticed that in the Remediation Center, the target machine's maximum timeout time before a system shutdown/restart is 100000 seconds, and want to increase it even higher.
The maximum timeout for a manual remediation shutdown is 100,000 seconds, which is more than 27 hours. In normal circumstances, this should be enough for users to finish their work.
If you want to allow users to decide when their computers would be rebooted, a good approach is to choose a "Let the user decide" option in Auto-Remediation options After Deployment settings. Users will be able to define themselves when the reboot should occur.
Please be aware that if a reboot is required and has not yet been done by the end-user, LanGuard would still keep on showing the patches as pending remediation.