extendLV =
#(define-music-function (further) (number?)
#{
  \once \override LaissezVibrerTie.X-extent = #'(0 . 0)
  \once \override LaissezVibrerTie.details.note-head-gap = #(- 0.2 (/ further 2))
  \once \override LaissezVibrerTie.extra-offset = #(cons (/ further 2) 0)
#})

\relative c' {
  \extendLV #2.5
  e8 \laissezVibrer r16 r8
}