Been working with #pantheon a good bit here is the answer to a common question of how to update your WordPress site.
The process we use is to create a multi-dev instance, perform the updates, then run the QC process after the QC process we push to the dev and test instance and do a final QC in test because that environment should always be running your live site’s data.
1. Try to do it after hours so no interruption and in case anything happens. Also
2. Make sure to make a Multi-dev of the live site right before you merge. Pantheon restores can take a LONG time and your site is down if something goes wrong. Merges can happen pretty quickly.
If you have any questions feel free to reach out to us for an answer.