Herbs Sanitized Before Drying?

I have questions about drying and keeping calendula (chrysanthemum):
1. Some chinese herb shop told me that all their chrysanthemum (included calendula and marigold) have been sanitized before drying by using steam. Have you ever heard about this? If yes, then what is the process?

Some Chinese herbs undergo special treatments prior to drying and storage. It could be steam, boiling, heated sulfur, or other processes. For some herbs, sulfur is heated under screens on which herbs have been spread; the sulfur helps to preserve herbs or prevent them from discoloring over time. Steam and boiling treatments are used to bring out the medicinal potency of the herbs, or to change its medicinal effect. Korean ginseng is a good example: steaming the roots causes the roots to change to the characteristic deep red colour favoured by Koreans, while the Chinese prefer the unsteamed white form of the root.
Usually such treatments are done on plant parts that can withstand the harsh treatment, parts such as the roots or stems. I doubt that many delicate herbs such as chrysanthemum or calendula are treated this way. I suspect that your Chinese herb shop is exaggerating the extent to which these treatments are applied to herbs, as a marketing ploy. If delicate herbs such as chrysanthemum and calendula are grown and dried in a clean, non-polluted location without use of uncomposted manure to fertilize the plants, then the resulting dried product should not need to be "santitized". In China, however, unsafe growing practices and pollution can be a problem, thereby necessitating special post-harvest treatments.

2. I would like to know is it okay to keep all my dried herbs inside the freezer?

If the herbs are stored in airtight containers to prevent the build up of ice then there is no reason why dried herbs cannot be stored this way. Freezing may extend the shelf-life of herbs, but we are not aware of any data that prove that.