Walking to class I heard a difference in the tap between my shoes — one sounded louder, like the heel cap was worn down to the metal stick. So I got back from class and changed out the cap. Neglecting to replace heel caps (whether on low heeled boots or any high heel) will ruin a pair of shoes, and you can often replace a high heel's cap by yourself. In fact, I'm picking up my favorite pair of boots from the cobbler later today — I had the heel caps replaced and a rubber sole added because leather soles need extra protection if you want to wear them in rainy weather.
See the complete DIY here.
The plastic is so ravaged because getting it off usually takes a few minutes of tugging with pliers. If you have a workbench with a vice grip attached, the process is much easier.
I had two heel caps I took off a pair of shoes I don't wear, but you can also buy them in various shapes and sizes at shoe repair supply stores. Once you stick it in you simply press the heel against the floor and let it slide in.