ANSWERING MY OWN QUESTION:
After 3 weeks of trial (tried compiling an index with two volumes and then with three), it appears that to compile an index of the size and complexity we are doing we must let the book sit and compile for at least a week. When we forced a shut down it showed InDesign was not responding, however that was a deceptive message as the program was actually working.
Here is a sample of what the index is compiling. It is not just words but pages and pages of the below:
A.M.H.C. v. Ciereszko (CA)  1 SCR 157, 4 WWR 1, 143 DLR(4th) 1, 8 CPC(4th) 1
Gray v. Dow Corning Can. (Sask)  6 WWR 185, 48 CPC(3d) 50, affd (CA 1996) 48 CPC(3d) 50n
Perpetual Executors v. Comm'r. of Taxes (HC Aust) [1949} ALR 461, 23 ALJ 144, 77 CLR 493, quoted  AC 114
And of course the program must do a comparison and find duplicates and then put the page number for each incidence.
So, if anyone out there is trying to do something of the same sort, do not necessarily believe the message you get when you start Task Manager and then look at what the program is doing. If it says the program is not responding that may not be the case. It cannot respond because it is actually processing the request.
Using Indesign CS5 operating Windows 7. 897 GBs of space on hard drive. Have a large book (4 volumes) with the 5th volume being the index. Index once run will be over 800 pages. This is an encyclopedia and is heavily indexed. Previously used old Ventura program which was able to handle the index volume. However, when we attempted to run the index using CS5 the program ran for 3 days and ultimately crashed.
The question is, is this document too large for Adobe Indesign to handle? Would like to know now before we are ready to actually run the table again.
We are able to run an index for a smaller 2 volume book which is also heavily indexed, no problem.
Message was edited by: Deborah Lewis February 16, 2016 2:09 PM