If he doesn't take vacations it's ok. It's his choice so, if he's ok with that there are no problems. My advice is: use your vacations, always.
There are a lot of reasons to use that:
You need time for you and for your family, spend one or two weeks for a holiday is something you have to do in order to recharge yourself.
If you don't use your benefits, you could start a vicious circle. Your colleagues could start to think that you are refusing a benefit just to appear a better employee. It happened to me and was a bad situation.
In some countries the vacation days are taxed so if you don't consume these days your company will pay a lot of money. I don't know if this can be applied to your country but in Italy (my country) there are several taxes your company have to pay for vacations days you don't use.
