I don't know if the programs already do this but I think they would be much harder to track down if they included some randomness. When they see someone refreshing every six seconds on the dot for 2 hours its pretty clear, but if the aber refreshed randomly between 5-7 seconds, it will be hard to find a patern. As well as that, perhaps have a list of secondary items that arent critical and if there is nothing important to buy, try to buy one and put in an incorrect price? Also, if you have less important items you could take slightly longer to buy it. Finally, rounding numbers to their easy to type equivalents before entering them would really add to the authenticity.
most ABers already refresh at a random rate between x and y seconds ^_^...but the problem with rounding numbers is that legit RSing has to be done real fast to beat the ABers so most people type things like 33333, or 12312...
maybe making them refresh roughly when the shop restock, like for example, refresh from 1-25 secs, the again from 45-60secs. that way it not always refreshing