why do I have to readjust the bed anyway?

Do you use binder clips? They warp the glass more than you think and this can make you think your bed is unlevel. Source: I was a noob caught in this trap.

Tighten the leveling screws as far as they will go while keeping the bed level. I made a modified z stop for the SD4 so you can use a longer screw if needed. If you print it at 100% infill, it is sturdy enough that the force of the bed will not bend it and mess up your first layer; I have seen this happen with my stock z stop unfortunately. They tried to counteract this with a spring but it doesn't work.

It also helps to let the bed sit for a few minutes at temp before printing so everything can undergo thermal expansion and "re-align".

If you are over extruding, your bed gets knocked around a lot and this can contribute to falling out of level.

Overall your bed should not fall significantly out of level, I only have to balance mine once a month or so now.

Lots of info, hope it helps. The bed leveling systems is one of the reasons to not print directly on the kapton. You should see what scraping a print off can do to your perfectly level bed even if you're careful...

If you are having to re-level your bed there is a good chance the rivets or some other part of the platform that is loose.
I haven't leveled my bed in over 4 months.

I would recommend adjusting the 3 leveling screws as tight as you can get them without having the bed hit the platform.

If you are referring to adjusting the z-height adjustment then look for something that is loose in that area.