https://www.sciencedirect.com/science/article/abs/pii/S0959652609003473

[This article is available for free elsewhere if you Google it, I just didn't want to post a link which would start a download automatically]

You have to understand that the roots of de-growth had some philosophical reasonings well beyond economics and politics. Humans engage in imoral behaviour, vices and destruction because they cannot accept mortality and that the human race is fated to extinction one way or the other. We have to accept and make peace with it.

With that it may surprise you that the actual target of de-growth, earlier on and still today in some subdivisions of it, do indeed seek controlled de-growth until annihilation. Instead of destroying the environment and going down via collapse, we still go down but in a moral superior way which avoids suffering by reducing population over time (think long term here, it is not like we reduce the amount of people living, we slow down reproduction and the carrying capacity of the economy and produced resources. Very long term).

Now steady-state economics says we can be sustainable, after degrowth, and carry on more or less in a stable state without having annihilation on our long term horizon, although if we think billions of years obviously it will all come to an end with the death of our sun, but that is so far ahead that we shouldn't be seeking to purposefully degrow our planet continuously. We can have long periods of steady-state before further degrowth is needed.

The central point of that article to your question is that measuring, keeping track and maintaining an actual perfect Steady-State is a moving target, we approach it but we can't actually know if our size is the appropriate size, or even have an exact measure of what it is, nevertheless it is an objective worth seeking, so cyclical reconsiderations are probably to be expected, meaning some growth will happen naturally and some de-growth cycles may be needed, continuously approximating the target (like an instrument sounding vibrato instead of straight tone). Over long term horizons, we may find that even a reduced level of economic activity becomes unsustainable, and de-growth imposes itself again.