You are missing the point. The time is chosen by the makers of Limewire as the time it takes to search a very large network for sourses. There is no point in having the feature running for say 60 seconds. It would not have enough time to search the network properly!
I do not understand why you want to make it a shorter time ... but then my signature sums up my feelings
You can always "kill the download" if you want it out of the way.