Yes, that's quite like what happened to the first pair I lost heels from. I bought them on December 28th, had the plastic bits at the bottom of the heels replaced around the 10th January (already a bad sign that they needed it so quickly), and then both plasticy bits fell off on Monday in a falling-down-stairs-with-one-heel-caught-in-trouser-turn-up incident (which also involved spilt coffee). Luckily, they only cost £25 (probably the root cause of all the trouble), so I don't feel quite so annoyed about giving up on them.

It sounds like the people who reheeled your pair in October are more worthy of return custom than the people last week... unless they are actually the same people?