Reduce faces

fluffy82

I did a quick search on this, but didn't seem to see an answer. If it is out there, sorry for posting it again and thank you for directing me to the correct topic

I am building a model of a building which I want to become quite detailed, especially the columns/capitals/architraves/...
There are many extrusions and to enhance the level of detail, I used 48 or 96-sided arcs as a basis for each one of them.
The model is growing larger than I expected though, so I need to reduce the file size for it to stay manageable (to give you an idea: I divided the model over 6 separate files each holding part of the building; each of these files is between 20 and 45MB large...).
The obvious way - to start with - is to reduce the number of faces on these extrusions.

Is there a way to reduce them without deleting the whole thing, drawing new profiles using arcs with less sides and extrude again?

Thanks!