I also have MBAM Premium with real-time protection. So I don't see a point in doing manual scans like Threat scan. I don't do manual or scheduled scans with my AV either because of its real-time scan. The only time I do one is before making a new system image backup, but it's probably not necessary then either. If it would find anything, it's probably not anything dangerous. Otherwise the real-time scan would've detected it.
With the exception of a manual scan finding an executable file that real-time previously missed, because of updated definitions, but then I'm already in trouble.....
For being a security enthusiast, I am very surprised you take this route. I would think you would know better then that.
I'll try to explain it better then:
I missed to explain the possibility of other benefits with a manual scan, like heuristics. Besides that I see no point in for example scanning all files in a manual scan. The most important thing is to scan all files used in real-time. Other files shouldn't pose any danger even if infected. As long as they are never used they pose no threat, and if/when they're used the real-time will check them.
In my experience, the only time a manual scan has detected something that real-time hasn't:
- an executable file type that hasn't been used/run lately (due to updated definitions)
But if it would run after the definitions were updated then the real-time would pick it up
- an non-executable file type like zip (but if a process would've used the infected file in the zip then the real-time would pick it up)
- a heuristic detection (this might reveal something "bad" but has higher risk of false positives)
But I rely more on my AV's HIPS protection than the heuristic detection from a manual scan
Note: This is based on experience of my AV. How exactly other AVs work with heuristics and HIPS (and detection rates) I can't say, or even if they have those features. Unlike many others here I wouldn't for example recommend MSE to anyone.
PS. I should also add that I'm more cautious than the average user and check downloaded files on VirusTotal and HerdProtect before using them. I often also do manual scans on the downloaded files to get the heuristics checked. And I check the digital signatures too. First time I launch a new program I check it in Process Explorer to see if it's a packed imaged which is unusual and more suspicious. I also check all DLL's the program uses(lower pane VirusTotal check in Process Explorer). If it's not a commonly used program I launch it through Sandboxie the first time.
Haven't had an infection in years and that's why I only do manual scans before creating new system images, like A Guy, I just don't do it as often.