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:

 1. 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.
 2. 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.

 

 1. 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.