This is what I've been doing for years, but Heroku Postgres is so bloody expensive, it just doesn't make sense for apps that don't make much money. So I just moved my data to an RDS instance, shared between multiple apps. Cost savings are great, headache savings much less so. I would say if you are going to move off Heroku, do it with the apps/projects where you can f-up, or have downtime without much repercussion. AWS stuff is a deep dark forest, undocumented and confusing. I'd say for anything that is critical, just keep paying Heroku. It isn't worth it.
