Friend of mine works for a scientific equipment lab (mainly various kinds of microscopes and simulation equipment), and spends most of his time maintaining and adding features to Smalltalk images. It's an inhouse Smalltalk developed in the early 80s.

Some clients still pay to have their machines that run off 8" floppies maintained and upgraded.

Bear in mind, that for this sort of work, a contract can have timelines like 10yrs to implementation, with 20yrs support thereafter.

EDIT:

To expand, and try and answer your question a bit more thoroughly...

Smalltalk can be painful at times, and he vastly prefers C++. Especially a Smalltalk that has a completely different idea what file systems should look like, and how serial ports should be treated.

This old Smalltalk doesn't allow exceptions to happen on IO, which creates a large amount of debug-hell at times, though at least with Smalltalk the boilerplate is limited.

However, despite ten years of cruft, and fifteen different project leads, the projects are still manageable. That is a huge mark in Smalltalk's favour. There are other languages where this is possible, but it usually requires a lot of discipline.