Step 10 is continuous. Using driving as an analogy to life, it is a good idea while driving to continue to watch where you are going.
In step ten we continue to watch for dishonesty, selfishness, fear and resentment. When they crop up we take immediate action, for which we are given clear directions. It is very much an in the moment thing, not to be deferred till next week, next month, or an annual house cleaning.
The reason, as far as I can tell, is it is far less painful to deal with an injury as soon as it occurs, than it is to wait and let it fester and grow and infect our soul. Like removing a sticking plaster, a quick tug is less painful than slowly pulling it off.
When to work it in terms of progress through the steps? Well it seems this is the one step you are given permission to work out of order. "Vigorously we commenced this way of living AS we cleaned up the past" Not after. For my own experience this seemed logical as I realized that while I had a huge pile of garbage from the past to clean up, it would not be until I was well into the process that my mind and attitudes would be healed to the extent that I would not create a whole new pile in sobriety. My alcoholic mind did not just disappear when I stopped drinking. In fact it was my behaviour when not drinking that set me up for the fatal first drink.
I found it a total life saver to keep the decks clear by "cleaning up any new mistakes as I went along".