How Many Rec Letters Is Too Many?

I’m a current junior and with this upcoming summer supposedly being the most important summer in my high school career, I’ve applied to four summer programs. For the letter of recommendations, I’ve been asking the same two teachers, over and over again, because all of the programs I’ve applied to are science related and I only have two science teachers this year.

Is it okay to ask a teacher for ~5 rec letters? I want to apply to more programs, and the only thing that’s holding me back is my fear of asking teachers who have already submitted 3 letters on my behalf to submit several more.