Depends on the ale, serving pressure & the size of the hose. If you have 3/16" hose, 6 feet works well.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk
Its a Belgian Wit hoping not to have to change hose lengths too often.
Thanks for the Info
The hose length in a kegging system depends on the pressure drop rating on your line (x lbs/linear foot) and the pressure you have on the keg. My line has a rating of 2lbs/foot of pressure drop. Since I almost always pressurize at 12 psi, I need about six feet of hose to balance the system.
If you change your pressures quite a bit, adjusting your hose length can become a pain.