This is the FTTC/FTTP forum, so it's safe to assume we're talking about FTTC, which typically has far shorter line lengths than the 4000M you suggest. Some of lines of less than 100M, 200M, 300M etc is quite common.
On VDSL2 and G.FAST etc, every meter counts.
Increased attenuation, by using meters of cable as you suggest, will result in a higher attuenuation than without it. For some lines, this can make a big difference. For other lines, they might not notice a difference.
My 0.5M Twisted Pair RJ11 cable cost only £2.99 - worth every penny for my line at least.
Edited by dave2150 (Fri 08-May-15 00:29:33)