you actually made me curious and i decided to find out who has been an advisor more than once (please correct me if i missed someone)
only taylor swift and scott hendericks have been an advisor 3 times even though taylor only helped michelle in the top 6 in s4 so you could say that is just two.
other two-timers are ed, miranda, ryan, lionel, reba, and charlie
another fun fact: only 5 coaches haven't been an advisor on the show before