I've done more than 500 hours on the standard setup, including ABS PLA and Ninjaflex, so I don't think you need to replace the whole thing.

Regarding the thermocouples, if they look like this image, they need insulating. Personally, I would leave on the originals, as they won't be very different to the new ones. Thermocouples don't vary anywhere near as much as thermisters.