Flash backs are a trip into the past of a story. If poorly used they interrupt the story's flow. Too many occurring and the story loses impact and slogs rather than sings. If your story may need only one or perhaps two looks at the past, they could be skipped as not needed or even brought out in a bit of dialogue.
If you're going to have several longones, you may be taking a chance. If it 's needed for the present in the story tomake sense, you'll have to find a way to slip them in. Remember if these are scened the action has already happened and you'll need to find a way to make it vital. The character has won or lost in the past. To make the flashback make sense what you need to loook at something else. Why did they win or lost and will this pattern continue in the present. Has the character learned from the past ways to make changes in the future.
Flashbacks must be interesting and expressed with a vitality that doesn't distract from the current story. If they're going to be present throughout the entire story, they must be as fresh and as vital as the current events in the story.