You can enable auto-recharge or upgrade to one of our retail or enterprise packages. We would also highly recommend you consider moving to an annual package, because you will get a full year's worth of credits immediately (and those credits do not expire until the end of your yearly billing cycle).
Pay-as-you-go credits purchased through auto-recharge have the benefit of not expiring. However, we're continuously adding new features, so your credits won't go to waste if you upgrade your monthly subscription!
If your needs exceed the number of credits in the available enterprise credit packages, you can email us at account [at] localfalcon.com for a custom pricing package.