Well, some people can't help going on weekends, and as long as you accept that the waits are long then (especially July/August) it isn't a problem. If you know it's coming it won't be as likely to ruin your day! To answer your question, the waits can range from 5 minutes to 2.5 hours depending on crowds, weather (good or bad), time of day (midday is worst, usually), if other major rides are shut down for any reason, etc. Really isn't a guessing game for the most part about how long the lines will be, just be prepared to wait and be pleasantly surprised if you don't have to! :)
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Po!nt of View: A different look at Roller Coasters.
http://www.crosswinds.net/~justmayntz/thrills/index.html