Microsoft has been consistent with firmware updates for the Surface Pro since the release of the device back in February of this year, with the exception of just one month. However, Surface Pro owners are still experiencing a bug that causes the device to sleep after a few minutes of idling, even when the power options clearly specify a different power plan.
"One of the software issues I've been experiencing is that when my Surface Pro first goes to sleep after a restart and I wake it up, it then begins going into sleep mode every like 1-2 minutes of being idle. I noticed this when reading some news on the internet. I double checked my power options I have my current power plan (based off Balanced) set to put my Surface Pro to sleep (while plugged in) after 30 minutes of being idle!" one user stated on an official Microsoft support forum.
No matter what the power plan is configured to, the Surface Pro seems to enter sleep mode within a few minutes. A few suggestions appeared on the support forum asking users to change the power plan, and even disconnect/reconnect the power supply, to no avail. Microsoft's solution to this problem is to do a system refresh or complete reset of the device, which isn't a practical idea.
While Microsoft hasn't clearly identified this as a bug or offered a solution just yet, there are a few methods that may work for those of you who are experiencing the same problem. The first solution involves resetting your security policies (User Accounts > Reset security policies). This is because of an addition of email accounts to the Mail app in Windows 8, causing certain security policies to be enforced by Exchange and resulting in the computer locking after a few minutes of inactivity.
Some users have tried adjusting the settings in the Group Policy (gpedit.msc > Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options, Microsoft Network Server: Amount of idle time required before suspending session) and found that adjusting this setting didn't fix the problem for some users but it did fix the problem for a few. So try this Group Policy method to see if it works for you.
You can also head over to Control Panel> Administrative Tools> Local Security Policy> Local Policies> Security Options> Interactive Logon: Machine Inactivity Limit, and adjust this setting to a greater value to see if it helps.
For those of you who are experiencing this issue, hopefully the above suggestions address the issue. If not, lets hope Microsoft rolls out a firmware update in the near future that does fix the issue. Let us know in the comments below if you have had this issue and if you found a temporary solution to fix it.