There are a few usage limits for email campaigns.
Email campaigns you can have active at one time: 8
Desktop product widgets per active email campaign: 2
Mobile product widgets per active email campaign: 2
Image widgets per email campaign: 2
HTML widgets per email campaign: 2
Served campaigns per email: 2
Served recipients per LimeSpot subscriber per minute: 200
If any of these limitations are exceeded, the elements will still render, but render with a latency as they will have a lower priority.