File sizes:
Bkgds: 6 MB
Working: 700 KB
Plotting: 140 KB
There are 2 vports through out 9 layouts:
1 shows flr pln
1 shows design notes
In working files (x-1mech, x-2mech, x-1plum...) there are 4 xrefs each:
x-1flr .................. x-2nd
x-grid ..................x-grid
x-found ................x-framming
x-2nd ...................x-1st (shall be overlayed)
That is a large architectural background, I'd be try to reduce that file size by eliminating entities that you do not require ie:dimension, door & window no. etc. arch drawings contain a lot of stuff that you may not require and sometimes you can reduse their dwg by half.
Since you have 2 viewports per layout, 1 containing floor plans and the other notes. Have you frozen the un-neccesary layers in your notes viewport? ie:you arch is on layer name 'xref' use 'vplayer' or in layer manager freeze items in 'current viewport'
This will eliminate a lot of processing, & with your limited RAM you need to do this.
As CADaver has said in the old days that may have been fine, but as time passes new versions of windows & acad etc. gobble up all the computers resources leaving nothing left. Hence the crashing out or the time it takes to process drawings. Your plotting file is affectively a 12+meg file so every time you change layouts & plot your computers resource run lower & lower, hence it get slower as you go. With files of that size a ram up date is in order.
Otherwise you need to look at everything to limit the size of your drawings.
clean out all un-neccessary architectural items, purge & purge again until nothing left to purge.
use 'overlay' and not attach' when xrefing
freeze layers within your current viewport. (particularly your notes: viewport) think about putting your design notes in paperspace rather than a viewport. (I take it that you design notes, are a general notes: column & note drawing notes with leaders pointing to your drawing entities) If they are typical notes per drawing, maybe you can create a notes dwg & xref them into paperspace instead or make them part of your title block.