What happens if you never ever run e2fsck?

We have servers which have been running for a long time. When they reboot, we see this message: kernel: EXT4-fs (sda3): warning: maximal mount count reached, running e2fsck is recommended My question is: what if you never ever run e2fsck? Man page does not shed enough light. The warning message says "is recommended" - but does not say it is mandatory. What are consequences of not running it? What does it mean to have maximal count reached?