Running Avast for the first time and so far it's been churning away for about 4 hours .... How long should a full scan take? (I've a tri partion 120G drive).
Seems normal if you ask for 'high' sensibility (scan archive files). But, as you may imagine, it depends on your CPU, RAM, disk rotation, size and type of files, etc.
I won't worry too much if you're clean.
Does it restart after finding a virus?
No, it can be repaired or send to Chest, or deleted...
You can delete on next boot time but, better than all, try boot time scanning. This will be better for what you're looking for.
Rigth click the skin and schedule a boot time scanning
PLUS any other general tips you might have,
Well, will be impossible to give you tips... There are so many... Why don't you start a trip into the forums? Are you brave? See 'Settings' and discover how much avast can be configurated