Once your management pack XML(s) are completed, the must be sealed and signed into .mp files to package ship to customers. As a best practice, no individual .mp file should be larger than 10 MB.
Large .mp files mean that customers must deploy this large file to every agent in their management group, which can be a very performance intensive operation. Also, it should be noted that it is a CSS supportability criteria that any .mp file should be less than 10 MB.
If you are developing one large MP that contains all class definition, monitoring, views, reports, and covers all scenarios, consider breaking your MP up into separate files. For example, one approach would be to have separate files for discovery, basic monitoring scenarios, advanced monitoring scenarios, and reports.