Hey Slumerican! You should definitely familiarize yourself with Psychonauts.com. They have developed a huge and from what I can tell, pretty reputable library of substances, their effects and how long said effects may last. If you are interested, simply click the link above. I've found it to be an awesome resource over the years both for assisting my peers here at BL and for my own use too!
If you were to ask me, I would say you're entering into a more moderated experience. You're not going to be tweaking out of your mind on 30mg followed by another 30mg several hours later. You will feel and understand the way that the drug works including most likely, a comedown of mild-moderate intensity based upon how you hydrated and otherwise took care of yourself throughout your stimulation.
It varies, yes, but an oral dose of anything is going to range in time of absorption due to variables like stomach content, acidity etc. You'll almost always begin feeling the slow absorption of the drug begin by the 30 minutes mark.