alMaddul Aslee are only lengthened 2 vowel counts and then the madd muttasil is 4 or 5 vowel counts. This means it is only double of Al maddul aslee. How come most reciters stretch it for much longer?

Question
Assalaamualaikum warahmatullahe wa barakaatuh

I am confused with the lengthening of the madds.  For example  alMaddul Aslee are only lengthened 2 vowel counts and then the madd muttasil is 4 or 5 vowel counts.  This means it is only double of Al maddul aslee.  How come most reciters stretch it for much longer?

Answer
Wa alaikum assalaam wa rahmatullahi wa barakatuh,
It is true that the natural lengthening is two vowel counts and that the medd al-Muttasil is four or five vowel counts, but we do not hear many reciters lengthening it more than that.  A vowel count is based on each individual readers speed, how long they are taking to make a vowel-and all vowels should be equal in length, then that count is multiplied to obtain the proper length of a longer medd. 
If a reader is reciting slowly, then his/her medd lengths are longer in timing-as far as seconds on a clock, than a reader reciting quickly.  Each reader though, is reading the longer mudood the same number vowel counts in theory- but their vowel counts are not equal to each other because of their individual speed. 
Of course, everyone is human an may make an occasional mistake, but in general the readers are lenghtening correctly, but their speeds vary and thus the length of their individual vowel counts do too.
Wa asaslaam alaikum