Pansies seem to do best when temps are below 75 degrees. They will also start to straggle and under produce when light levels are too low. If they're spindly, cut them back by at least one-third... or farther. That should stimulate new fuller growth and more blooms later.

Many people remove them when they begin to fade out in the heat, and replace them with a favorite summer annual for color into the fall. It depends upon your location, too. If you are in the South, it's really not worth trying to keep your pansies alive through the summer.

From what my grandpas tells me if you trim them back and leave them be, they will bloom again in the fall. Mine are starting to do the same as yours, and I plan to trim them back this weekend to see what they do. I think I am going to plant something around them to draw attention, but that is blooms in the opposite season so there is always some color there.