Repair and upkeep is in Wonders of the Lost Age (the book with all of the artifacts that need to be repaired, naturally).<br/><br/>The rules for maintenance are not ... uh, they're not actually well-explained.  It's suggested that maintaining artifacts with a repair rating, most magitech, requires a significant time and resource investment, otherwise they will start to break down.  It's not very specific about how long that is supposed to be in general though (my understanding is that the writers of this book, like so many Exalted books, decided not to ask each other what they were doing, so the ones writing maintenance decided 'welp, they'll include artifact-specific rules for each artifact' and the ones writing artifacts were like 'welp, they'll just write general maintenance rules for everything', and the result is there are no meaningful rules for most cases.<br/><br/>The book suggests that maintaining magitech is expensive and time-consuming, though, so that seems like a reasonable approach.<br/><br/>Repairing broken magitech is an (int+craft) roll, the same as whatever was used to build it, against a difficulty of the Repair rating (if it's 1-3 dots) or rating^2 if it's a 4+ dot artifact (which becomes an extended action.)  If an artifact breaks, you need to make an Int+Lore check to see if you can figure out how to fix it.  (WotLA, pg 6-7)