Can I stay on Drupal 7 forever? I've been using Drupal 8 for a while now and while it's not bad, it does slow down development a bit, as the whole framework is more strict. Which is a good thing to some, but I know of many people like me, who prefer having the freedom of easily creating modules, versus having to set up the new folder structure etc.

So my question is, can one survive without upgrading for the foreseeable future? And what is the longest time one can realistically go without upgrading?
IF the current version of Drupal is working out for you and you don't need more features added than you can stick around on 7 for a long time.

The problem is that D7 will not receive any feature updates and most modules will not be updated for D7 aswell. 

It is hard to say the exact date of when D7 will not be supported anymore but most likely in 3-4 years.

but the bug/security fixes will continue till the end of this year most likely.

source: https://www.ostraining.com/blog/drupal/drupal-7-end-of-life/