Does the lifespan get shorter or longer ? Maybe i misread this but i read again now that in buddhist view life span will become shorter and shorter until 10 year life span 

did i misunderstand somehthing ?  it seems that the lifespan is getting bigger and not shorter
In Buddha's time the life span is said to have been 100 years and there were several theras who touched even 120 years e.g. Ananda and Maha Kassapa. In fact Bakkula thera is said to have lived 160 years, he had ordained when he was 80. But we rarely hear anyone passing 100 at present. 

A well-respected monk in Sri Lanka (late Ven. Nauyane Ariyadhamma) has mentioned that the life span reduces by 10 years in each millennium. Judging from that, the 10 year period should occur roughly in 7500 years from now. Who knows what can happen within this period.

The causes of illnesses and therefore, the reduction in life span according to Buddhism is mentioned in Cakkavatthi sutta. 


  Thus, brethren, from goods not being bestowed on the destitute poverty grew rife; from poverty growing rife stealing increased, from the spread of stealing violence grew apace, from the growth of violence the destruction of life became common, from the frequency of murder lying grew common, from lying growing common, evil speaking grew abundant, from evil speaking growing abundant, adultery grew common, from adultery growing common abusive and idle talk grew common, from abusive and idle talk growing common, covetousness and ill-will grew common, from covetousness and ill-will growing common, false opinions grew common, from false opinions growing common, incest, wanton greed and perverted lust grew common, finally from incest, wanton greed and perverted lust growing common lack of filial and religious piety and lack of regard for the head of the clan grew great.
  
  From these things growing, the life-span of those beings and the
  comeliness of them wasted, so that, of humans whose span of life was
  two and a half centuries, the sons lived but one century.
  DN 26


The essence of this is that for the life span to increase, human qualities also have to improve, advances in medication and increase in the standard of living alone will not be enough.