日語 Japanese Ask Questions Thread2 質問

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Japanese - Ask questions thread
http://dis.4chan.org/read/lang/1174719097/l50

Is there a difference between してて, してって and していって?
I saw the first one in a manga as 「安全にしてて下さい。」 I don't remember where I've seen the second one. The latter I've only seen in 「ゆっくりしていってね！」