Oh, crap, I don't have regular Skype installed. I just clean installed 14291 yesterday.
If you are "testing" the insider builds, but don't want to have the next build dropped on you until you're ready for it, you can limit upgrade downloads by reducing the amount of free space on your drive, either by shrinking your partition size, or by transferring files of a sufficiently large combined size to your insider test drive volume, so that a 2GB ESD download would fail.
I guess you would have a chance to hide that update, skipping it until the next build that you actually want to download using KB3073930 - Windows Updates - Hide or Show in Windows 10 - Windows 10 Forums - after you have released the space on your drive to be able to complete the download and upgrade.
On insider accounts, you aren't limited to just one insider build, you can have several - whether they be Fast, Slow, or Release Preview ring, or all three rings on a single or multiple machines - real or virtual - therefore you don't leave the insider program, so much as postpone it on one of your build installations. Perhaps that is why some of the insiders here can switch between rings on a build with ease?