Btrfs and balance

To find out whether you need to run balance, just have a close look at the output of
sudo btrfs filesystem usage /path

    Device size:		     476.44GiB
    Device allocated:		 252.04GiB
    Device unallocated:		 224.40GiB
    Device missing:		     0.00B
    Used:			         224.00GiB
    Free (estimated):		 250.86GiB

And compare the difference between "unallocated" and "free", and "allocated" and "used". Snapshots can play a big part in this.
The higher the difference, the more it is likely that a balance operation can help.

You should not run a full balance, since it will rewrite almost everything, potentially leading to SSD degradation. A factor of 50% might be a good starting point.

EDIT: after a balance of 60% on the above, I get this:

    Device size:		     476.44GiB
    Device allocated:		 245.04GiB
    Device unallocated:		 231.40GiB
    Used:			         223.99GiB
    Free (estimated):		 251.86GiB

Notice the difference.