The biggest problem with long primaries and trying to add fruit is beer loss due to there being a lot of tub and sediment you are trying to secondary ferment in the primary. Even adding fruit to the boil is problematic for long primarying. Speaking from experience, for example with a pumpkin ale I tried that on, you have a lot of goop that will make for a difficult racking AND bottling experience. Taking the beer to a secondary or even a tertiary before bottling will help leave that sediment behind.
There's no problem with adding the fruit to primary, but I would then rack to a secondary for a week or so to let all the fruit goop settle out, when that fermentation is complete.
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