On one recent post a user mentions about his scan running for hours. I think he had got up to 19 hours and it was still running, surely this cannot be correct I find a full scan of 2 hard drives takes about 40 minutes.
I accept that the more programs you have plus the type of processor has a bearing on the time a full scan takes but there must be some point when you decide that the program has got into some continuous loop and will never finish ?
The other topic we think there is some confusion to say the least in what is going on (is also avast 4.8) so I believe unrelated to this question.
We will need a lot more info, OS, CPU, RAM, Sensitivity, if archives were selected (in fact and change to default settings for the Full scan), the amount of data on the two HDDs. So as you might see we can’t answer your question without more info.
The first few times you run avast scans it is also building up its Persistent cache database, this is used to speed future scans for files either in a white list, etc.