They will shut down your instance, if you don't use it for an hour or two - and then it will take like 8-10 seconds to load it again. If you can live with that, I guess that would work, yes.
From what I see, when you have a single dyno, Heroku deploys you to a different environment sandbox called "development". Typically that has less uptime and takes lots of upgrades all the time with interesting consequences. I believe they promote to "production" applications much less frequently.