horst,
Great question and one that I think probably has many good answers.
Here are some of my thoughts. I think the answer depends upon things like, how much time you have to hunt, how many years you have been hunting, how much game you've taken, the age structure of the bucks where you hunt and how you will feel after you have shot the buck.
For me personally, which is how I am interpreting your question, if I don't want to put the buck on the wall I don't shoot it. I try to avoid the mindset that I've got something to prove to somebody else.
At this point in my hunting career I look for a buck that I think is at least 4 1/2 years old and has character. It is more fun if it is a buck with which I have a history. For example one I've previously seen, taped, found the sheds of, etc. The last 4 bucks I've taken I've seen at least twice and two of them I saw at least 6 times. I was able to get tape of all four live, one of them a year before I got him and many times the summer before I got him.
The catch with hunting 4 1/2 year old bucks is that 4 1/2 is also the age where they really start to get hard to harvest or even see sometimes, but, that is what makes it a sport. The bucks that have meant the most to me are the ones I had to work the hardest for. Some of the most memorable were bucks that I hunted for years and never was able to take.
I've also learned a few lessons the hard way. One is if I have to try to talk myself into thinking a buck is big enough to shoot I will most likely be disappointed when I walk up to him. So now, if in doubt, I don't shoot.
I still cringe when I think about a few of the bucks I've shot over the years that had great potential but I took them too early.
I also try to keep my focus not how big a buck I shoot but how much fun I have being out there. I'd much rather spend a season outdoors, see and video tape lots of good bucks and shoot none than to take a high scorer the first time out if I had to be done for the season.
On the other hand, you can only pick from the bucks that are available in your area. During one time span, some time ago, I went 7 years without shooting a buck. Every year I saw and passed lots of bucks including some nice ones. I finally realized I was waiting for something that either wasn't there or was way too smart for me so I lowered my standards a bit.
Great question. Those are some of my thoughts. Ultimately, you have to make up your own mind...every time you see a nice buck walking your way.
Good Hunting,
Old Buck