Straight from the horses mouth.


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Do our characters (my character and my recruit's character) have to be same level in order to receive triple experience?

No, but you must be within 4 levels of one another and meeting all other triple experiences requisites in order for both characters to receive triple experience. If this level requirement is not met, only the lower level character will receive the bonus.

For example: Should your character be 5 levels higher than your recruit, only your recruit's character will be eligible for triple experience (provided that all other requirements are met, as well).


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http://us.blizzard.com/support/artic...rticleId=25716



Also look for the following message.
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How can I tell if I'm receiving triple experience?

Triple experience will be noted in your Combat Log as follows:

"Player gains 'X' experience ('Y' exp Refer-A-Friend bonus)"

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Hope this helps.

Hope this helps