Crack in wall... best DIY repair method?

I live in an old house with plaster walls and when I moved into it over 30 years ago there were quite a few large cracks in the walls and ceilings due to the old folks who lived here prior not maintaining it.

I established that the plaster was stuck well to the wall and not loose, I dug out all the cracks to clean out any loose debris prior to mudding and taping.

I used regular drywall mud to cover the cracks and then put the fiberglass mesh tape over the mud and bedded it in. Once that initial step had dried, I came back and skimmed over the repair to make it blend in well with the rest of the surface for a more even look. In some places this took 2 passes to get it to blend nicely.

I did this over 30 years ago and over that time only a couple small ones have shown back up-----and I did at least 200 ft. of crack repair throughout the house back then.

Gumbo showed you the way.
Keep in mind that this is a movement crack and it may or may not reappear. Nothing you can do will prevent it. All you can do is repair as instructed and hope for the best.

My home is pier and beam and I have a crack like that...sometimes.

Cold and dry I have a crack...warm and wet and you can't see it. My house moves.

I've not been able to prevent it so I just live with it.

Maybe the flexible caulk as mentioned above.

Does your wife like above-the-door decorations?

Doors and windows are going to be the first areas cracks appear with settlement. Probably not an issue, but I would also just pay attention to what's going on in the area outside the home. Is water draining away from the home? Is the area staying saturated?