Most people use pucks which is chlorine with stabilizer (CYA), the problem is the stabilizer doesn't go away and just continuously builds up over time. The more build up, the less effective the chlorine is.
So most people are forced to shock their pool hard every 2 weeks since the chlorine can barely do it's job.
Once I get my pool open, I never shock it during the season. I just put my 1/2 to 3/4 of chlorine daily and sometimes raise or lower the pH about once a month. I use Liquid Shock because it is cheaper, it is basically Chlorine but higher %. If I'm in a pinch, I will use bleach but I have to use more than twice as much as liquid Shock.
I typically buy 16 bottles of shock and that lasts me 2-3 weeks. Then I stock up another 16 bottles. Opening and closing I will use up a lot more.