If you have a free Heroku instance, you might sometimes face a long first page load time on your web application. This is because Heroku will shut down your instance after a while if nobody visits your site. This is a problem I have encountered with Bill Splitter since my girlfriend and I were the sole users.
There is a simple way to fix that: curl or wget the website every few hours. You can place the command in a cron job and you will never deal with a slow first page load again.
It’s not the nicest thing to do since you are abusing a free service, but it does fix the problem.