Effects of various anti-aging therapeutic scenarios on a typical individual who is in middle age when the therapies are initiated. The red line indicates the default trajectory of accumulation of damage (or, equivalently, loss of reserve) in the absence of therapies; it should be stressed that this is for illustration only and that we make no assumption that the rate of this process is linear with age. It is presumed that there is a “frailty threshold” of loss of reserve, beyond which intervention becomes much harder as pathologies are emerging and exacerbating their own rate of progress. Blue line A therapy that halves the accumulation of damage (until it reaches the frailty threshold) but leaves pre-existing damage unaltered. Green line A therapy that initially halves the accumulation of damage and whose efficacy is doubled every 7 years, but which always leaves pre-existing damage unaltered. Pink line A therapy that removes half the damage. Orange line A therapy that initially removes half the damage, but 20 years later has been improved so that it removes half the damage that it previously could not, and undergoes the same improvement every 20 years thereafter. Note: colours appear in online version of this article and in reprints available on request