Install time seems excessively long
Setting up a test ElCap and the time remaining went from a few minutes to a few millennia according to math, the install will be ready in the year 3907.
MacBook Pro, OS X El Capitan (10.11.5), 2011
You can always abort and try again.
I have always found the estimated times to be wildly inaccurate.
Install time seems excessively long