How long each part lasts

Biology replaces almost every component while the whole persists. Computing replaces the whole while the components outlive it.

v3 revised 2026-09-15 Column format with imagery; the two ladders read down together. v2 ›

Read both columns down, shortest first. The pairing is positional, not causal — a bacterial division and a memory refresh are each simply the fastest thing on their side. What the two ladders show is not that the numbers match, but that they run in opposite directions.

Lifeparts are disposable
Computingwholes are disposable
Milliseconds to days
~20 minutesBacterial divisionUnder ideal conditions. The fastest complete self-replication anywhere in either column.
~64 msDRAM refreshState survives only by being continuously rewritten — the closest computing comes to metabolism.
3–5 daysIntestinal epitheliumThe lining of your gut is younger than your last holiday.
hours–daysA container instanceIn anything autoscaled. Deliberately disposable, and the one place we copied the pattern.
Months to a decade
~120 daysRed blood cellsNo nucleus, no repair, a fixed service life, then recycled for parts.
~2–5 yearsA major framework versionBefore migration stops being optional.
~1 yearMost of the liverReplaced wholesale while never stopping work.
3–5 yearsServer refreshThe depreciation cycle, and the SSD endurance rating. Both are accounting decisions as much as physical ones.
~10 yearsThe skeletonRemodelled entirely. The thing you think of as most permanent about you is on a decade cycle.
15–20 yearsA data-centre buildingThe longest-lived physical asset in the column, and shorter than your bones twice over.
A lifetime and beyond
a lifetimeNeurons and cardiomyocytesThe exception that explains the rule. The cells holding state that cannot be reconstructed are the ones never replaced.
~15 yearsTenure in the S&P 500Churn in a ranking, not corporate mortality — a company usually leaves by being acquired, not by dying.
~73 yearsA humanGlobal mean. Persisting while almost every component is exchanged underneath.
~45 yearsTCP/IPThe oldest thing still running essentially unchanged. Our most durable artefact is a protocol, not a machine.
10⁶–10⁷ yearsA speciesBefore extinction or divergence. Varies by orders of magnitude between taxa.
no counterpart — nothing in computing is old enough to have a lifespan yet
What outlives what
inverted
A human body replaces its gut lining every few days and most of its cells within years, yet persists for decades. A company's servers last about five years — and the company itself now lasts around fifteen. In biology the parts are disposable and the whole endures. In computing it is closer to the reverse.
What these figures count
counts
Typical replacement intervals, not maxima. Corporate tenure is time in the S&P 500 index, not company age.
excludes
The bands order by duration; they do not pair by kind. The alignment is positional. Nothing is claimed about a container being like an intestinal cell beyond both being short-lived by design.
uncertainty
Index tenure is a forecast, revised repeatedly: Innosight's figures fell from 61 years in 1958 to 24 by 2016, with ~12 projected for 2027, while other trackers put the current figure nearer 15. Species lifespans vary by orders of magnitude between taxa.
the trap
Index tenure is not corporate mortality. A company leaving the index has usually been acquired or has shrunk, not died. It measures churn in a ranking — a proxy for disruption, not a lifespan.

Continuity through replacement

Biology solved a problem computing has not. A body maintains identity while almost every atom in it is exchanged. There is no migration window, no cutover weekend, no version freeze. Replacement is continuous, piecewise, and invisible from outside.

The mechanism is the one the energy page is about: every component is maintained by ongoing expenditure, and anything that stops being paid for is recycled. Persistence is not a property of the parts. It is a property of the loop that keeps replacing them.

Note the exception, because it is the tell: the cells that mostly do not turn over are neurons and cardiomyocytes — the ones holding state that cannot be reconstructed. Everything reconstructible is disposable. Biology replaces anything it can regenerate from a specification, and preserves only what it cannot.

That is a design rule, and it transfers directly. A system whose specification is written down can afford to treat its running parts as consumable. One whose behaviour lives only in the parts cannot — which is why an agent architecture that keeps its spec in a document and its state in a ledger is not bureaucracy. It is the thing that makes the components replaceable.

Sources