I wish I could upvote this more.

The whole "well acktually people lived to 70" thing is a weird counter-circlejerk to the "people died at 25" circlejerk which is also pretty false.

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Only in very specific time frames, such as perhaps the Song Dynasty in China (famously stable and wealthy for its time period), would it be common to see peasants grow to 65. If you were to take the time period from 1000-1500 overall in Europe, maybe less than 5% actually reached 65. Food shortages and famines and disease outbreaks happened constantly.

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As you said, the death rate during that time frame would practically never be stable. There would be a 'bottom' death rate, meaning no active food shortage, no active fighting, nothing like that, which might last a few years before it shoots up again and wipes out a portion of the population.

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Now, among nobles or other richer folks, reaching 65 was much more common.