Genuine Dyson DC07 post filter pad

When would this part need replacing?
After the motor has failed
When the pre filter has not been washed often enough causing this filter to block too.
Will fit DC07 models below:

DC07 Standard, DC07 All Floors, DC07 Allergy, DC07 Animal, DC07 CLIC, DC07 Full Gear, DC07 Full kit, DC07i grey/red, DC07 Origin, DC07 Tool kit, DC07 HEPA, DC07 Precision, DC07i


NOTE: picture shows DC14 filter as filter is compatible with both DC07 and DC14

Genuine Dyson DC07 post filter pad