It took me ten years but I finally got my hands on a soldering tip cartridge at a Metcal repair station (STTC-140 to be exact). Considering what I went through (including soldering PL-259 connectors when it wasn't the ideal tool for the job), he's soldered at least 300+ PCBs from bare to finished (a very conservative estimate), and that does not count. all the repairs and wiring I did on it before I bought my butane iron to work on cars. He doesn't owe me anything and I'm still more than happy with the device. I just bought an identical tip to replace. Ten years ago I said this would probably be the last soldering station I would ever buy and I meant it. These cartridges are a big reason for that.