I just did my first full scan with Avast 5 and it seemed to take a long time, nearly 50 mins. I have a pretty basic setup with Windows XP home, IE8 and Firefox. I am guessing with the first scan Avast is getting familiar with my configuration and building up the cache and subsequent scans will be faster?.. :o 
Short answer yes.
Use persistent caching - if persistent caching is used, the information about the scanned file is stored in the permanent memory. This means it is not lost after a system restart and it is also not affected by virus definition updates. Consequently, persistent caching is suitable only for files which are guaranteed not to contain any virus infection e.g. operating system files, files signed by trusted publishers, or other files covered by the avast! whitelist. This box is checked by default; if you want all files to be scanned regardless of their trust status, this box should be unchecked.]Use persistent caching - if persistent caching is used, the information about the scanned file is stored in the permanent memory. This means it is not lost after a system restart and it is also not affected by virus definition updates. Consequently, persistent caching is suitable only for files which are guaranteed not to contain any virus infection e.g. operating system files, files signed by trusted publishers, or other files covered by the avast! whitelist. This box is checked by default; if you want all files to be scanned regardless of their trust status, this box should be unchecked.
Thats what I was guessing. People at Wilders have mentioned that they love the permanent caching…good to know. I’ll be getting a Pro license this evening to get those other great bells and whistles like the sandbox, cheers… 8)
Get the pro trial version and have a play with it first, that gives you 30 days unrestricted use before having to pay.
I’ll give that a try…thanks for the suggestion… ;D
You’re welcome.