Too little material may provide protection for a while, but need to be replaced regularly.
By the 1970s passenger services were being regularly replaced by buses.
The carpeting is regularly replaced every few years, whenever it appears worn, according to the office staff.
Batteries for the radio and flashlight should be replaced regularly.
It should be replaced regularly or everything it has removed may be released into the system.
They could be renewed by turning them over, but had to be regularly replaced.
The infusion set must be replaced regularly, usually every 2-3 days.
The argument that e-readers will be regularly replaced is overstated.
Many died in transplanting and had to be regularly replaced.
Remember that your toothbrush should be regularly replaced, at least twice a year.