I have a dedicated tap and two rotating kegs for seltzer.
30 psi for 4-5 days is good for carbonating. Then I move it to 8-10 psi and serve. It doesn't lose noticeable carbonation at the lower pressure.
I also did an experiment where I cut a length of beer line just long enough to reach the refrigerator door (3ft, appx). Bubbly water still pours out.
Water is really different than beer inasmuch as foam and head aren't factors. My minimalist system works great.