I am sure that many user of this printer found that the printhead is hopelessly problematic. I have changed two printheads since I bought it. And it is not cheap! So, I will document it here what I learnt in order to extend the life of the printhead. The information are shared to me by the service engineer.
1. If you use power clean, do it once only. More power clean will damage the head;
2. Always use normal clean. If the head doesn't seem to improve after two cleaning, switch it off and let it rest for a few hours or overnight;
3. Print as often as you can;
4. Don't switch off the printer even if you are not using it;
Practicing the above, I found that clogged printhead is less of an issue.
Last tip:
If the paper never load properly after the paper had unloaded, just use a scissors to snip off a triangle piece from both side of the paper.
Please comment here if you have any other tips.