When rebuilding individual archives, Movable Type splits up the rebuilding process into segments, where each segment consists of rebuilding N entries. The default value for N is 40, so by default, MT will rebuild 40 entries at a time, then move on to the next 40, etc. You can change that value globally here; for example, if you have a very stable server, you might wish to just get it all done in one batch.

Default value: 40

Example:

    EntriesPerRebuild 100