Question: How many updates / bulletins can be added when a Software Update Policy is created.
Answer: There are no limitations, for the product will work as designed if the environment is able to support the load. As the environment grows over time, more and more bulletins are downloaded and Software Update Policies are created, and the load becomes more heavy.
However, Support has found the general best practice is not to exceed 100 Software Updates. Keeping in mind that each Bulletin contains multiple Software Updates.
Points to consider when creating the Software Update Policy:
Caution: Anomalies in targeting have been found when the same Software Update Policy is used for different deployments. It appears the targeting source code gets corrupt when all of the bulletins are swapped out, and the guids and resource associations are not updated. This is not a reproducable BUG; however, the misbehavior has been seen by support and therefore it is recommended to disable any unwanted Software Update Policies, allow for all targeted clients to update configuration to receive changes in policy status, and then delete the policy. Create new Software Update Policies for each bulletin package deployment.
Avisory: As of October 2016; Microsoft has changed the Software Update delivery method to include all monthly releases in a Cumulative Monthly Rollup as outlined in INFO3895.