I plan on continuing subscription to support Unreal Engine as I can, but if for some reason in the future for awhile the subscription ran out, how would I re-install the main binary version (not the source code version) of Unreal Engine 4 and related Tools if I reformatted my main development computer erasing everything and re-installing everything, and is it possible to do so if the subscription ran out?
look …if you need my opinion.
make a backup for the engine via DVD…I think nothing easier than that :))
Read this post … it will clarify to you 
Unfortunately, that could probably create some bigger technical problems further down the road if I went that route. To prevent conflicts and versioning issues or registry missing entries or mixed version settings or files, my thoughts and hope are I’d probably just follow the download link to launcher, login through the launcher as my online account would still be valid, select the version that would be displayed at time when subscription expired, then re-download that version of the software. I feel that would be the best approach, but I need confirmation if that would in fact be how to handle it.
I just came across this post Keymo42 that was listed in the Related Questions section on the right side of this webpage at time of this last posting, apparently, if I have any problems I should contact billing@epicgames.com and they’d send me direct links for Windows or Mac, etc… and would be able to download any versions that I paid for, if true that would be the awesomeness thing ever and I do think they care about their customers, this is why I’m glad I choose Epic Games tools for developing my game(s):
https://answers.unrealengine.com/questions/32882/cancelled-my-subscription-i-cant-download-anymore.html
Yeah I found that one too.
This is correct, and we are still looking into ways to improve and streamline our processes.
Cheers