Using separate repo for Ember and backend (Rails)

I’m going to use separate repos for front-end SAP and Rails. Rails will only serve API. Tests for Ember app will use mocked data.

Up till now I have had Ember app as a subdirectory in Rails app. Using the same repo is easier to maintain. Having a separate repo for backend detaches the two.

Is it worth to keeping them separate? Can deploying be a pain - building from two repos?

App will hosted on Heroku.