Question about XZ compression

hello Debian,
how big is the compression result/file size difference between XZ Utils's
first version and its latest version and have you been planning to compress
sshd with liblzma and inject the liblzma library into the software when XZ
is updated enough or are packages compressed once with XZ and not again
even if XZ is updated?
I feel like I needed to make my question more clear and I'm trying to look
for a definitive answer