Longevity Training must be done in multiple Paragon Houses to get the full benefit, in Records, under Mastery there is a tracker iirc.
That said, it ain't going to be enough on its own, there are multiple way of going around it, all of them grindy.
You can bring either Wildbrook, Harmonized Settlement, or Cave Cultivation to around 1 Qi per year.
You can go to the Wilderness and farm some Insight (each one gives a multiplier to Lifespan bonuses).
You can get more Harmony Bands (Balanced affinity on multiple of 10, 10 being 1, 20 being 2, ecc), as that apparently gives more lifespan as well (I think the only reference to this is in the later game, unless I missed it). This appears to not be true, and I can't find the reference to it anymore, my bad.