Shunts last anywhere from days to decades, something like 30 to 40% don't last a full year, ~40-50% don't make it to two years out. Revisions happen for all sorts of reasons.. infections, obstructions, valve is not ok for patient (flow, other characteristics, etc), and so forth. Know the signs of shunt failure (can happen intermittently), all the signs as every patient is different. Other common problems are under draining and over draining , many issues that younger kids have are different from those shunted at an older age.