SharePoint 2013 my site takes longer time to load

I've implemented the spswakeup powershell script on the environment to make the first visit of the SharePoint environment a bit less painfull (spswakeup.codeplex.com). This is really a solution to load my SharePoint intranet faster, even if the first user visits the SharePoint.

The issue is now that at random times, the My site still takes 15-30 seconds to load, even if these are in the spswakeup script too (visits all sites and site collections in the web applications).

My feeling (but I can be wrong) is that this mysite takes longer due to a connection to the Active Directory or something like that. Is there a tool or a way to test this? Or does anyone know what else this can be?

Thanks in advance!