Why are most elected members only elected for 5 years and not for life time?

It is because Citizens cold observe the developments taken place and if they think that the ruling party is not working properly, the election after every 5 years give them the chance to choose a better representative.It gives people to change their choice of choosing the right representative.

the answer is solomon northrup. he was a free-born african american, abolitionist and professional violinist that was drugged, kidnapped and sold as slave in 1841 and remained in captivity until 1853 where he regained his freedom with the of the then-governor of new york, washington hunt. he wrote and published his memoirs "twelve years a slave" in 1853, and in this text, he tells the story of his escape thru one of louisiana's swamps (the great pacoudrie swamp) in which he ended up covered in green slime from crossing the surface of the dead water.