Interesting question for you. I've created a dashboard I plan to use as a template and just swap out the data at the source; right now an excel file. I've been able to port over the new data source using a few methods I found here on the forums but now I can't create an extract of the new data source or all my views take +30secs to load. I take off the extract and they zip right along at < 8secs easily.
Any ideas as to why this is happening? No dimension labels changed and new source data has approximately 10,000 less rows and about 5 less columns. Nothing here indicates to me that it should take MORE time to calculate the views let alone seeing an increase of 30 seconds for simply turning on extracts.