It's hard to know how much, it's all about the final scene. Your performance will depend on your hardware, on game engine you use (native or html5 ?), on the dimension of your images (width/Height/optimization), the size of the files... And all other objects, events, and the way you are using it. There is no "hard limit" on number of sprites from what i know, it's just a matter of feeling.
During a development, always focus on performance and optimization from the start. Also ask yourself why using so much images in a sprite ? Maybe the animation can be smooth enough with less images ?