Note also that - at least as far as I am aware - we have not managed to extend lifespans. Erastothenes for example lived till 82, at or more than the current expected lifespan of many western and first world countries. We have only increase the probability of arriving near the maximum life span by dealing with famine, war, diseases and optimizing diets and nutrients and lifestyle.
That said, is there any way to know if we've increased the maximum lifespan? It seems that accurate birth-date records in many parts of the world didn't start until the 1900s, as there's even difficulty 'verifying' the oldest person in the world today.
You're probably right that on the top end we haven't seen a ton of progress though, I think that first we have beat the things that tend to kill you in old age (cancers!) before we'll start dumping major resources into actually preventing the damage from aging itself that causes us to top out a little after 100.
Hopefully we'll also manage to reap an affordable vaccine or cure for malaria and some of the nasty diseases of tropical poverty in the next 20 years too, which will help that average skyrocket even more.