Here's a couple tricks I use to make scrubbing sponges last longer, I usually buy the big pack when they are on coupon/sale at Costco, the pack literally ends up lasting a year or more. It always feels good to save money but I love it when I can consume less and throw less into the landfills, it's a win, win!
Cut them in half, I generally don't use the whole surface area when I'm cleaning, it's usually just a corner or an end to scrub something that is stuck on so I don't lose anything by cutting it in half.
Wash dirty sponges in the top rack of the dishwasher. If the scrubber part is still in good shape but it's starting to get a little sour, just put it in the dishwasher the next time your run it, comes out fresh and good as new.