Blending with existing paint


Promoted Users
Have not a lot of repairs where I will need to blend on existing paint job. The paint job was fresh last year and I am fixing a spot that had bad blistering or Solvent pop. I took it back down to primer and repreped the area. My question, the spot I'm repainting is about a foot in diameter, how big of an area should I blend to on the existing paint? I was going to prep the existing paint with 600 and currently planning about 6-8" blend with existing paint.
Thank for Any advice...