Execute change set task doesn't wait long enough

The Execute change set task only seems to wait for 60 minutes for a cloudformation stack to finish updating. This should be higher (or be configurable) since CloudFormation will wait 90 minutes for a CloudFront distribution to complete.

Start at the Execute change set task entry point and locate the timeout used while waiting for a CloudFormation stack update. Confirm how the current 60-minute limit is enforced, then make the wait accommodate CloudFront's 90-minute completion time or expose that limit as configuration; done means the task waits successfully for longer updates.

Written by the indexing model from the issue text.