How can I make sure to never run out of credits?

If you want to make sure that this never happens, there are 3 ways:

• Pick a plan that has slightly more credits than you expect. This way, you’ll always have a buffer for busier times.

• Upgrade when you notice that you are running low on credits (e.g. when you receive a notification email at 80% of your budget) and downgrade when you don't use your monthly budget.

• Have some Pay-as-you-go credits as a backup. They are only used when all of your subscription credits have been used before (in which case you receive another notification via email).