GA Connector fields such as Pages Visited List and All Traffic Sources can sometimes get too big if a user visited too many pages. This causes some server errors such as ‘Request Header Or Cookie Too Large’, 400 Bad Requests, etc.
To prevent this error and cookies from getting too big, we have set a 255 character limit to the tracking values that we sent.
Also, most CRMs have a default character limit of 255 for their custom fields.