Hi Berra,
How big is your project area?
The next release has some decent performance improvements for map gen times, as well as an option to increase the initial grid size (currently always 1m), which can also dramatically improve map gen times and reduce memory usage, usually without any significant loss of detail. There is also an option to make a copy of an existing project (or user map), which will be useful for splitting maps into smaller areas; create a map project with your required tracks and settings, then make one or more copies of the project and set the map area of each to a sub-region. We haven't done anything to automate this part of the process, but it is an idea we could look at.
To export a map with a number of sections, you can either create each one as a separate AT5 file, or do as Greg has suggested and export the shapefiles for each and combine those in a single run of the IMC. Another alternative is to add all of the components to a single user map and export that, or add each section to a separate user map, and export all of these maps at once - which will result in a single AT5 map.
Matt
