Do you use traffic exchanges?

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If you use traffic exchanges. As you must have seen most of them give manual surfing only especially the top rated ones like easyhits4u. My real question is did ever joined any site that you come across while surfing or commented a blog while surfing? I want to know because i spend my time surfing for credits but do i really gain anything more than impressions. I have signed up many times even commented 10-12 blogs.