It depends on the man, his stability with himself and life, and also how well he can handle household chores himself. Some men just flat out die when they lose their wife after a lifetime together. Some men pull it together and make some choices, like do they want to stay where they lived with their wife, or move to a retirement community. Sometimes couples make that decision together, so when one is left alone, they don’t have to feel helpless and alone. I have known a couple of widowers who just passed away soon after their beloved with no medical cause other than they just felt done. I have met many who are lonely, and suffer with wanting to be more, or do more, or just be gone, but they don’t want to be over.
As @jerv said, don’t let him be alone.
When I came to Fluther, I was feeling lonely, and sought advice. I got lots of very good advice, but, being lonely doesn’t get helped much by things like bowling with the girls, and lunches with the girls. At home, in the evening, when I am home, and alone, and nobody walks in all muddy saying, “Mom, I need these pants for school tomorrow.”, that is when I feel it. Those are the times a widower is going to feel it.
If your Dad takes up with a lady right away, don’t be upset with him. That often happens when oder folks find themselves all alone and unable to cope with an entire night of nobody talking, nobody else brushing their teeth, nobody laughing at the same stuff on tv.
If you can stay overnight from time to time, or for a while, that would probably be great. If not, then the best timed phone calls would likely be just before he gets ready for bed, and/or right after he should be getting up.
That is when the emptiness tends to hit the hardest.