1.) No scan needed after each session. Real-time scanning differs from manual in this one important aspect: Any file or executable is scanned in the background automatically, at the moment it is run, and without user intervention, when it is called for and run on your system. Think of it this way; avast! is already doing all your scanning for you without you having to do anything. (See point #4)
1a.) PUP’s are Potentially Unwanted Programs. Because they are categorised as software that can be used for good or ill, antivirus programs do not block installation of them automatically, and thus allows user discretion as to whether the particular program should be on their system or not. It’s up to the user, not the antivirus program, to decide.
2.) Boot-time scanning can be dangerous to your system. Use it only when recommended by avast!. Always quarantine, never delete, if the first option is available. Otherwise, choose ignore and quarantine, if possible, later. Windows system files should never be deleted or quarantined, even if infected. Come here for help if you encounter such a situation. Otherwise, you’re looking at a damaged operating system and one that may not boot again if you choose either one or the wrong option.
http://antivirus.about.com/b/2007/03/11/clean-quarantine-or-delete.htm
3.) User decisions and choices affect the integrity and validity and safety of Windows to a far greater extent than some users realize. Visiting adult sites, using torrents without educated discretion and choices, running cracked software, visiting poorly rated sites, etc., all of these, and more, affect whether or not your system will remain clean after a session, or any session, for that matter.
4.) A/V’s cannot protect the user against everything out there. New malware is created every day, every hour, and every minute, to get around a/v defences. Both manual scanning and real-time scanning are both ineffective against this strategy created by miscreants every day.
Heuristic scanning helps, but the highest level brings with it the risk that a known clean file will be tagged as infected when it is not. That can be a problem you can do without.
5.) Two add-ons (extensions) for every browser you use is recommended to complement a/v protection:
https://www.mywot.com/
https://adblockplus.org/en/firefox Tho the link is for Firefox, if you look by the ‘Install for Firefox’ green button, you’ll see other major browsers are supported and protected by AdBlock Plus.
-WOT covers point # 3. WOT blocks poor sites, and also rates software distribution sites, so you can decide whether you want to visit, or if it is safe or not to do so.
-WOT also helps with point # 1a.
-AdBlock Plus helps cover some of point # 4. It blocks malicious ads and adware code so you will never see them in your browser. Plus, your browser will load a page much faster whilst protected, as much less junk is called and allowed to run in your browser window.
To sum up, real-time scanning is noted when a pop-up window pops unbidden in the lower-left corner of your desktop; it almost always announces that a file has been automatically been blocked to prevent harm or damage to your system. Manual scanning will find dormant and inert files on your hard drive (not running) that have data in them that may or may not match known malware signatures.
I’ve seen such manual detections occur very rarely, once in a blue moon, and most of the time, they are a result of a false positive detection.
Damage to your system can only occur when a malicious file is run. Damage cannot occur when a malicious file is not running and is just sitting there. The only time an inert malicious file can damage your system is when you open it, or when another system process is linked to it calls it and causes it to open and then runs from there.
It is primarily for the above reasons that manual scanning is much depreciated and of little value for protection from a safety security standpoint. If one wants an a/v that is only a manual scanner, think ClamAV. It offers no real-time protection whatsoever.
See my sig below for some ideas on what to run to complement a/v protection already in place.