Updating auto- expiration for time series collection

Hi all,
I am using timeseries collection to store sensor data defined/create as below

     new CreateCollectionOptions { TimeSeriesOptions = new TimeSeriesOptions("Timestamp", metaField: "SensorId", granularity: TimeSeriesGranularity.Seconds), ExpireAfter = TimeSpan.FromDays(365) });

As per the above syntax am expecting the document in the collection to be deleted after one year they were created.
Now due to certain requirements I want to change ExpireAfter to 2 years so the documents will auto deleted after 2 years since . how can I achieve this functionality in C#.
Any help will be appreciated .