How often do I need to replace the clove oil on my damascus steel katana?

Note: It is for decorative purposes, I do not actively use the katana

If its for decorative purposes then once ever 6 months to a year.

Usually your replacing if you practice with the blade, if its just sitting there and not getting dirt or wiped off through use, then its not as critical

Every 3-6 months you dont dith stains.

How often do I need to replace the clove oil on my damascus steel katana?

Note: It is for decorative purposes, I do not actively use the katana