If I want third party stuff, I download the .deb manually, and install with dpkg usually, then test, if it works that's great, if not oh well.

Sometimes I don't even bother with the .deb, like with Obmenu-generator I just put the executable where it belongs along with config files etc. It's kinda unique in that it only requires perl anyway.

I'm very slow in general to do updates, if it works in every way I want it to, I usually don't see a need to change that.

Anyway. I wonder if one relies heavily on various repos could we say that the more s(he) relies
on them them more (s)he misaligns with the distro used?
And then tasks like system updates or and general sysadmin and maintenance become more complex or error prone ?

In the worst lighting is as if a package act in accordance with a distro's house-rules but only to break them the moment it's installed.

My favorite analogy analogy in similar matter that i think is usefull in a range of similar phenomena (from emac's repos to appimages to containers) is that of a big house that accept regular guests. The initial owners have set a rulebook. Where to put your garbage , how to use common utilities , timetables etc. In that context  a container-like visitor would be analogous to bringing his own appliances (fridge, toilet  , library etc). It kind of remind me of a funny scene of the movie Coming to America with Eddy Merphie as a prince.

I think the discussion is usefull in order to calculate better the merits of each solution we choose.
For example when choosing a webbrowser or a programmming enviroment.