Well, I am a workaholic myself at this moment. It's not because a person wants to work for nothing but I guess he has a reason to do that. Who knows he wants to retire young as I do?
Try to discuss this issue with him. Don't put any pressure on him without finding first what's motivating him from working overtime. Whatever the motivation is, support him but also let him know that you want him to stay by your side. In my own experiences, my gf never ask me to do this or that. She always gives me her supports and at the same time I get a feeling that she wants me to have a little talk with her later on. In the end, I couldn't resist to meet her cause she's always full of surprises.
What I want to suggest is, try to understand who he is and accept him if you love him. Just go with the flow.
As what people said earlier, find something that you can share and spend time together. In order to have happiness you need to create it.
And here's a big huggggg for you and him.
