It is possible to do it over a few days really, even with not too much knowledge.

Requiring four months seems as if it was a side project, which is of course totally fine, but for any main task it really should not take more than a few days, even on a semi-slow computer (well, depends on how slow).

Well as mentioned it was in the 2000s. Compiling KDE alone took several days. Also there was no automation/script, so you really had to go to ftp.gnu.org and look in which folder the coreutils package is ;) I realize there's now a list of packages with checksums