Started around 2005 to consciously work on my energy system.
Since then it's beenf a constant growth and development process.
Even when (partially) opened, chakras can get (partially) blocked again because you live life, you interact with others, you encounter problems etc. etc.
It's not like you clear your chakras and that's it. It's also not like you clear your chakras 100% in one go. Can take years, or an entire life.
All depends what happened and happens to you, how motivated you are to keep working on it and so on.
Clearing and opening chakras is related to personal growth, working through problems you have encountered, learning from those, getting a higher vibration.
Apart from that, you get a chord from/with everyone you interact with. If you never clean those chords, your system gets cluttered (again).
If you keep at it, you can peel off layer after layer and get at deeper levels. (chakras and aura have layers, you can't really get to the core in one go, you;ll have to start with the outer layer).
Basically it's like cleaning your home: you don't clean it once and that's it. It will get dusty and messy again if you don't do anything for any length of time.
You may, however, find better ways to clean it, ways that work faster.
You will also learn that maintaining is better than cleaning house once a year.
All in all it's a beautiful process that takes time, so you best enjoy the journey.