Based on what chrome said, and your reply, I think you may have misunderstood him.
There are definitely times you will need to change the length of lead under your float. When I say LEAD I don’t necessarily mean just your fluorocarbon leader. Im referring to the total length of line under your float. For example, fishing a lead of 2’ will not be near sufficient if you’re fishing a pool that is 6-7’ deep. after much trial and error, ive found a system that works for me and is quick to change streamside. I use hi-vis line so ignore the shot line if you use clear mono. Float goes on the mainline. Directly under the float are a few split shot to cock it as soon as it hits the water. I then have a swivel to a 2 foot piece of mono on which I place all of my split shot. Follow with another swivel, then a 1.5 – 2ft piece of fluorocarbon. If I need to fish deeper pools I can simply slide my float up my main line.
If I find myself in a situation where I need to go shorter (really not often at all, as the river I frequent most often is primarily deep pools and runs) I simply remove the entire rig under the float, and just tie on a 1 or 2 foot piece of fluorocarbon and tie straight to that with minimal split shot all placed right under the float.
Hope that helps!