Ah, sorry, I mis-remembered what the feature was. The removalTime is only used when directly removing a facility, it isn't checked for building over another facility, only the buildTime of the previous facility is checked. In order to get what you want, the LARGE_GBUIDLING needs to have a buildTime much longer than 12 days - my suggestion would be to create a copy of the LARGE_GBUILDING with the long build time you want to speed up large facility placement, but not have it be built directly. Rather, have your current LARGE_GBUILDING leave behind this new copy when you 'dismantle' it.