One major advantage of low-technology manufacture is that repairs are relatively easy to make. If a surface gets worn, you either build it up by welding or patch it. A lot of welding gets done, which is easy due to the use of low-carbon steel. Eventually you do have to replace the boiler. The other major replacement item is the cylinder saddle, which can break and is not easily repairable. High cost item which can easily result in the retirement of an engine. Fortunately, this saddle doesn't break that often.