Ahmed,
The number of networks will be determined by the business requirements. Consider the below questions with your business:
1) How the project will be managed? Multiple project managers / sites / timelines
2) How are you defining your WBS structures? Phases vs cost buckets or both?
3) How would the network activities related to the WBS elements?
4) How many activities are foreseen per project? There might be a performance issue once a huge number of activities are selected.
So...go through these and decide what to do, because business always have an idea for how to proceed.
If the projects over 100 WBS will be repeated over time. Create a template project and network(s) connected. Use that template (standard structures) in CJ20N, to copy them to (operative) project and networks altogether.
regards,
Dave