Personally the highest scaffolds I have designed tend to be columns on the petrochemical sites. These usually go up to around 100m (50 lifts) and incorporate double standards up to a certain height and may require small bay sizes to reduce the self weight on each standard. It is possible to go higher than this as long as ties to the existing structure are available, the scaffold is braced correctly and the loads on each standard are reduced as much as possible using small bay sizes, reducing the number of boarded and working lifts etc.
I have also designed hangers dropping around 10 lifts inside a power station boiler and on the legs of a North Sea oil platform. As you can imagine the scaffolders do not like building these but sometimes there is no alternative.