Wait, what? I have never seen a kegerator with 10-20 feet of line running through it, so this doesn't make any sense (yes I realize this is an older thread). If I were to run my kegerator at 12psi to serve I would have a mess everywhere, therefore I must bring it down to "dispensing pressure" as you call it. There's no other way to do it, so I don't understand how I could be doing it wrong. There's not even anywhere in my kegerator for me to RUN that much additional beer line. I think that might apply to a bar/tasting room setup where the beer is coming from the cooler to the taps, but it doesn't add up when you're talking about a home serving setup. Can you expound?
If you set the serving pressure lower than the equilibrium pressure from carbonation, the CO2 will want to come out of solution, and will typically form pockets of gas in the line, creating excess foam on the first pour of every drinking session. Even if that doesn't happen, with each pour the carbonation will be reduced slightly, until it reaches equilibrium with the lower "dispensing" pressure. If you want to prevent foamy first pours, and maintain the carbonation level of your beer, you need to keep the serving pressure at the carbonation equilibrium pressure.
Most kegerators come with ~5' of 3/16" beer line. This is because they assume commercial serving parameters (carb level <2.8 vol and temp <38°). The warmer or more highly carbonated the beer is, the slower/gentler the pour needs to be to prevent excessive foaming. Since many homebrewers prefer serving temps around 40°, longer lines are needed to slow the flow down slightly and prevent foaming.
And 10-15' of 3/16" beer line coils up neatly on top of the keg, taking up hardly any room at all. From what I've read here, most of the brewers on this forum run 8-15' of line, so it's neither impossible or uncommon.
I think Kaiser442 was thinking 1/4" tube is ~1psi/foot, 3/16th is 3psi/foot.
here is a good write up from
beersmith
Those resistance figures are only valid for a flow rate of 1 gal/min. This is the flow rate that is assumed for commercial systems, and what you'll end up with if you use the calculators, equations and flawed advice in articles such as the one you linked.
While 1gal/min is the fastest a beer stored at 36° and carbed to 2.7 vol can be poured without excessive foaming, it's not ideal for most homebrewers. At warmer temps or higher carb levels, it's too fast and will result in foamy pours. The only side effect of extra long lines is very slightly slower pours, but they allow the user to pour beer at a wider variety of carb levels and serving temps. For a bar where the number of pints you can pour in an hour has an effect on profit, pouring as fast as possible is probably important. For most homebrewers, having a flexible system capable of pouring at a wide variety of serving temps and carb levels is probably more important.