Most people do not have liquid funds for years. I have cash savings, a large amount of CC, and borrowing power if needed. I just went through this, sort of; I suddenly had heart problems and needed to be off work for 4 months; even with disability, it was a close-run thing. Then, Open heart surgery stopped any work on a tank for a few weeks and slowed me down for a long time. Trying to talk my wife through a problem with auto top-off from the hospital was very difficult, as you can imagine. So please don't say "Grow up and behave reasonably." sometimes life just happens and you can do nothing about it.If anyone ever gets to this situation that they have to finance life from selling stuff from the tank, they have bigger problems, they need to grow up ASAP and start behaving responsibly.
I have liquid savings enough for years and I try not to have anything expensive in terms of money/time/space in my life or things I don't use daily, probably the two is not unrelated.
All my fish tank kit worth probably a few hundreds second hand and takes up very little space, so I don't see ever selling them - there is no point. Part of myself still don't like having them, cuz they are not necessities, but its a reasonably cheap hobby in moderation with a lot of satisfaction.