I'll try to sum up, please feel free to comment and/or edit if I misunderstood something:

• if a question is off-topic, it should generally be considered a candidate for migration or closure, no matter the age
• especially so if it has shown recent activity and was drawing attention unnecessarily
• for questions which are not explicitly off-topic but might have a better fit elsewhere, we have to consider the attitude of the community of the migration destination on this topic (do we have something in writing or do we need to get into their meta and ask when in doubt?)

I'll try to sum up, please feel free to comment and/or edit if I misunderstood something:

• if a question is off-topic, it should generally be considered a candidate for migration or closure, no matter depending on the age
• especially so if it has shown recent activity and was drawing attention unnecessarily
• for questions which are not explicitly off-topic but might have a better fit elsewhere, we have to consider the attitude of the community of the migration destination on this topic (do we have something in writing or do we need to get into their meta and ask when in doubt?)