Best Workflow for a large project

So I'm a newbie here, and also a rookie in terms of videography and videoedition (or is it video editing?) Just about a year ago I've started a small business with a photographer. We cover social events, such as weddings, corporate meetings, sweet 16 celebrations and so on. Since then I've been toying and learning with the application. The thing is now I have the exporting duties too. And boy it's been a tough ride. I shoot in HD and let FCPX ingest all the files also and start editing. The end project includes what one expects from a decent home movie, including intro, tittles, transitions, Fx and credits. The thing is that almost all my projects end being 2hrs but when I try to export the files are huge or better gigantic and it takes on like forever, almost 40 hrs each. I will gladly thank anyone who knows what's best because almost all the clients want their movies presented in DVD with chapters format. I've been following Larry Jordan, Ripple Training and PeachPit Press official Apple books on FCPX. Among others. In fact own some tutorials. Still no clue whats the best option. Help me in here pls. Of course I'll provide any specs on my iMac, and so on. Thanks.

Do you need Blu Ray or SD DVDs?

What is the format of your video; the codec you're importing? Give some basic system specs, ram. GPU. model, etc. Also, how are you exporting your timeline? And, as Ben suggests, are you trying to deliver Blu Ray or SD ?