I also care about being able to use the tool several years from now or on different distributions/OSes, etc.
With closed source you are locked to whatever the vendor provides, you can't just recompile it if it doesn't work on your OS anymore.
Also I don't have the time to reverse engineer and check the software for backdoors (not that I do that with the open-source one either, but at least its more obvious if something goes wrong there).
If you work on closed-source software then you probably don't care about this / doesn't matter there, but as someone who spends most of his time working on open-source software I definitely want my editor to be open-source.
If the vim developers announced next week they'd only support Linux, I'd keep using the Mac version until it becomes worse than a newer tool and then switch to that. The same is true of Sublime or any other text editor.
I'm not going to be forking an open source text editor if development stagnates.
Except that with an open-source tool you have the choice of using it as long as you want.
Once it is part of a distribution like Debian or Fedora it is unlikely that it gets removed just because upstream stagnates, and it'll keep running. If there are enough users the distros might even maintain patches of their own, or fork it themselves.
See for eg. tinydns, where the original is so old it doesn't even compile, yet there is a working version in Debian.
With closed source you don't have much choice except running an outdated chroot with an old distribution, or stop using it.
If you work on closed-source software then you probably don't care about this / doesn't matter there, but as someone who spends most of his time working on open-source software I definitely want my editor to be open-source.