Haven't had highlights that are THAT complex done, so I wouldn't know how they tend to come back with that much going on, but I hate throwing any more chemicals in the hair than necessary. I had to lighten my first two full caps and it didn't do the hair any favors.

That said, I used relaxer on my current full cap on the sides and the hair is still perfect after more than 4 months.

I'm sure the quality of the hair you start with is a big factor as well.