How big is big? 3 seconds seems absurd. If you upload every image under the sun, then no, this is not a good idea. You may also need to study image optimization (what format is it now? Can you post a sprite?)
In principle, this is a compromise. If you use 1/2 of the image in the sprite on your page, this is great because you get more gain through fewer HTTP connections and then lose unnecessary images. If you use 1% of the images in the sprite, this is not worth it.
- , , , . - . , - HTTP- 100 > 10, . 10- > 11 .