I was a big change-up caller during the meat of order, I would not hesitate to call 3 in a row and more. Every pitch the hitter was guessing would this be the fastball I'm looking for, it gets tough when your pitcher can consistently throw change-ups for strikes and hitter gets behind and has no choice but to swing.
Just remember those hitters that love change-ups, we had one on my DD 18u team that would take a change-up out of the park almost every time she got one.
My DD faced her in college and had a brain fart and actually pitched her one--SEE YA!