So how do alleged long term dopers (nameless in this discussion) continually manage to avoid detection?
How are they hemodiluting or getting a hematocrit within the parameters? Or are they just hovering at 47-49% and calling that their physio norm?
Hematocrit is easily manipulated by diluting the intravascular volume, and this can be done by overhydrating (whether it by with intravenous fluids or drinking copious amounts of fluids). Some riders, notably Ricco in the recent past, had TUEs for "naturally high" hematocrits but this is absolute BS for riders that do not live year around at altitude. A study from 300+ TdF riders between 1980-1986 (ie, pre-EPO) showed a mean hematocrit of 43% with a range of 39-48%.
However, hematocrit alone is no longer important. The biological passport uses other parameters to identify doping, such as reticulocytes (immature red blood cells). Reticulocytes are decreased with EPO for instance. So it is now harder to dope with EPO because the biological passport should identify EPO use. Should ... But team doctors, and even the results of the biological passport (at least according to Kohl), are used to fine tune blood results because they can monitor these internally.
In regards to your first question, dopers avoid detection because they are usually ahead of the testers. They stay ahead because of good doctors, good programs, and the cutoffs for the tests being set too high (for legal reasons) to catch the dopers. See Digger's post which details an excerpt from Dwaine Chamberlain's book about BALCO, drug testing, and a phone call with his doctor (http://forum.cyclingnews.com/showthread.php?p=48717&highlight=balco#post48717
). This is revealing and probably answers your first question well.