Clarification of antivirus scanning methods & Exclusions.

I seem to be going around in circles with this issue and would like to hear what other people think.

I`m using "Scan when Writing" only....is this enough or should I choose scan when reading and writing ? (or even just reading for that matter !)

Using Avira Free, although this could apply to any a/v....I would like to keep it as lean & fast as possible and was under the impression scan when writing would cover any possibilities, as any dubious files would be caught when being written ?

I`ve been noticing lagging when downloading/moving/copying large rar files of material that I know for sure is safe, but on the other hand don`t want to turn off archive scanning just in case.....

Maybe I`ve got it all wrong

The second part of the query is to do with Exclusions and Exceptions, namely defraggers, firewalls and any other programs that might need to be excluded.
Is there a generalised list of types of program that would benefit from being omitted from the realtime scanning process ?

Is this necessary at all, and should I be excluding the complete folder of the defragger (as an example) or just the process itself ?

(Avira only has a 15 character limit for process names.)

I simply wanted to know what solution would be least resource hungry, yet have a balanced level of security.

I do not go looking for dangerous sites, have additional security in Firefox but don`t worry myself to sleep over it....
I could simply restore an image with no problem if the worst came to the worst, no problem with that at all, but I would feel safer in the knowledge that I`m not making matters any worse uneccessarily

Although I haven`t been infected with anything for a very long time, and do regular offline scans with A2, MBAM, SAS etc.


Even considered going down the PrevX route, using that alone as it seems to be light from what I`ve read about it...but I spend time offline often when installing/testing and doing other things etc
not sure if that`s an appropriate alternative, and just dump Avira altogether or at least keep as an offline scanner.

All that turned out a little more lengthy that I wanted, sorry