So SVB & Earl have been using their extensions full time for some time now. Recently Jayson Shaw switched to his full time for the past 1-2 months. Now Mike D. just got one done by Mike Webb & using it full time as of yesterday.
Why not just get the cues built longer?
I say that people need cues that are balanced and proportionate to their height, arm length, and stroke length.
Earl and SVB are tall enough that maybe a 58" cue isn't the right length for them and they need a longer cue.
If you keep the same stroke length, a longer cue is either going to make your bridge longer or you are going to position your grip on the handle differently. The length of your arms isn't going to change any.
If you bridge at the flex point of your shaft and then add inches to the length of your cue, your flex point on the shaft doesn't change. Are you going to grip further up the handle to make up the difference or are you going to lengthen your stroke length?
I think it is a fad for most people. They see a pro using something and then they rush out to get one.
I wouldn't mind having a removable extension for my cue to reach long shots, but I don't think it would help me overall. I have short arms, a short bridge, and a short stroke length (compared to the newer players who have a 20 inch bridge and hold the cue at the butt cap)..