So, recently due to Gatlin's victory (at the age of 35) in the 100m Final at the World Athletics Championships (Why aren't you watching?), a chart came out showing the fastest times ever run by male sprinters and which times were writen off due to the athlete having a suspension for doping. Here: https://www.reddit.com/r/sports/comments/6ryan4/the_fastest_100m_times_ever_names_crossed_over/
This one for individuals, not the times: http://www.track-stats.com/drug-100m-the-fastest-men-and-their-bans/
With the amount of issue Athletics is currently having with doping rumours, even the association with it can cause issues (see Mo Farah and his trainer problems, Mo has proven time and again he's clean yet gets asked about it time and again), with how other sports like Cycling was once riddled with it so much so that no one won Le Tour for a few years, the state sponsors doping of Russia, the question is, should sports governing bodies perminantly ban players caught doping?
Of course it's maybe not as simple as a "you're out" scenario most the time, just look at Gatlin's second ban or Sharapova's very public ban (an only recently banned substance.... she had been taking for years). But maybe a possible solution to help stomp abuse is to ban them outright on a positive with chance of appeal. Dwain Chambers' case is a good one to look into because of how it not only affected him but clean team mates also, who got medals stripped because of his positive test.