I don't think they create a new ISO each time there's an Windows Update. I downloaded the ISO shortly after the final release and the Build 15063 was the most recent. If you'd like to verify that, visit the Windows Media Creation Tool page and download it again. To determine the build number, then follow the instructions in the link below to find and verify the build number:
http://winaero.com/blog/how-to-see-which-build-and-edition-of-windows-10-the-iso-file-contains/
Hope this helps.................
Grif
My understanding is, whether you want it or not, your going to get it. It can be delayed but not stopped. Since I had issues with the normal download process, I got the ISO and reformatted that way. While I had to reinstall everything, I felt very confident after words. And my PC has been working just fine ever since, about two weeks now.
Since I do everything for my sister regarding her PC, and since she is going on a one week trip next week, I plan to go over and do the ISO thing on her computer.
So, looking for a little confirmation that the ISO that I had downloaded, version 1703, build 15063, is “still” the current 'latest' version. I know there was a recent “hot fix” if you will, so of course that's where I'm coming from. I have a Dell and she has an HP, both are 64bit, and both have been/had been updated to windows 10 last year.
I have a 'detailed' write up on everything that has to be done, since from time to time I would do the reformate/recovery thing on my PC.
Thanks in advance for any suggestions

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic