That would be fine Matt, if all clients and remotes woke the MC Server again (reliably, in a timely manner) when they needed the next track in a Playlist. They don't. In fact, most don't.
It wouldn't matter so much if the Windows Sleep Timer is reset when MC serves another file. But it appears that may not be happening (not sure), and if so when the cumulative time since the first track was served exceeds the Windows Sleep Timer setting, the Windows PC will sleep. I tested a bunch back here:
https://yabb.jriver.com/interact/index.php/topic,123034.msg854575.html#msg854575, but I was using a Windows Sleep Timer of 1 minute for that. Maybe if I set the Windows Sleep Timer to more than the longest track in a Playlist, which is usually the case on my HTPC, the PC wouldn't go to sleep. But note also my steps 1 to 12, that eventually Gizmo stopped waking the HTPC, even though it should have kept doing that.
So there is an issue. WOL requests work for a number of times from Gizmo, and then stop working. I have no idea why that happens, and it is a separate issue to the Windows Sleep Timer setting.