One of the bigger problems is related to the fact that several AV companies release updates at least once a day or even on an hourly basis. This means that test results become outdated rather quickly, since the PCs used for such a test - 15x Pentium IV 2.8 GHz and 15x Athlon 64 3500+ - would require a couple of days to scan the whole collection, for just one scanner. If it took an average of one week per scanner (taking into account common problems like crashes and required restarts) we would need more than half a year just to test the number of scanners that are included in Virus Bulletin's latest VB 100% tests.