It really depends on the bric to its usefulness in old age and without support.
What does it do and use?
For example when Bootstrap moved from 4 to 5, there were a lot of significant changes that could break a bric that relied on Bootstrap 4 attributes. So any major changes with future Bootstrap versions may prevent you updating to the latest framework.
If a bric uses a third party library it may end up obsolete and with bugs left unresolved. A library can also be abandoned. Like what happened with Owl Carousel, not the bric, but the library itself was abandoned by the developer. Which was a shame, as I had used it in many sites, some are still online today as the client hasn’t wanted to update their site for years 
(non Blocs sites).
Major release versions do become obsolete. For example you wouldn’t make a website these days in Blocs 2, even if you didn’t want to use the latest features the framework it supports is widely out of date now.
Support can’t be there for your lifetime, it’s really the reasonable lifecycle of the product. And support usually follows the current version.
I was probably over generous in major revisions I have given free to existing users. Offcanvas Helper 2, would be an example. I’ve used native Bootstrap 5 and pure JavaScript, with no additional libraries, OH2 is very flexible and unless Bootstrap has changes around core offcanvas features, it will work for years to come.
But one day it will not work, either when updating Blocs or Bootstrap.
So end of the story, even though there is more to say, is that nothing will last forever. A lot of the variables are outside the developers and or users hands.
I remember having to make websites in Adobe Illustrator, slice them up and rebuild them in tables with notepad or dreamweaver. . Then do it all again for a mobile version and dealing with IE hacks. Heck I remember making BBS’ in the early 90s and created graphics with text . We had no idea what the future of the internet was going to look like then. I spent hundreds of hours creating and maintaining my BBS.
Love what you create, but don’t get emotionally attached to it is all I can say, because eventually it’s trash. 
PS. I’m sitting at a service centre waiting for our car, I have nothing to do but make long rambling posts on my phone. You’re welcome 
)