In my experience, to go from spring slime to totally clear takes a week AFTER 100% of the algae is dead, and IF you have a good filter setup.

You can do it faster with floc . . . but floc is unpredictable; everything has to be done right OR you can make it worse. And, you have to vacuum it out, JUST RIGHT. I found I was never able to depend on pool staff to do it 'right'; they'd get an a hurry, and re-suspend the stuff.

So, is 4 days too long? Nah. And if your cartridge is in crappy condition, or was a low-grade aftermarket model (ie, not OEM and not Wilbur or Unicel), it may take quite a bit longer.