Additionally to what Steffan said, if you've installed a custom pkg, you 
should put it on *hold* mode
with xbps-pkgdb(8):

# xbps-pkgdb -m hold <pkgname>

This will avoid updates with `xbps-install -u` and will have to be updated 
manually, i.e `xbps-install -u <pkgname>`.

For 0.44, I want to add a feature to only update a package if there's a new 
version in the same repository of
what was used for installation.