Reminds me, there are two different kinds of PTC.
Today's most common PTC is a polymer type, which is cheap and small, and very unreliable (100s to 1000s of cycles). They're only made to protect against single, infrequent fault conditions.
What if you need "unlimited" protection, or you have to protect something that's frequently switched (like a cycling motor or heater)?
Trick is to search for ceramic PTCs. 10k's of cycles.
Unfortunately, no one sorts them by type... so good luck finding them. Naturally, they tend to be more expensive, too, so you aren't going to find them in your usual cost-motivated search.
The Vishay parts are pretty reasonable:
Tim