Worth the Shelf

Buy It Once

Six questions to ask before you buy anything

The six repairability questions this site uses to judge anything: the wear part, spares, access, standards, post-warranty service and parts diagrams.

Updated 2026-08-27 · 886 words

Most things do not wear out. One part in them wears out, and the whole object is thrown away because that part cannot be reached, bought, or matched. This is the method the rest of the site runs on: six questions, answerable before purchase from a spec sheet, a manual, or a photograph.

What breaks first, and can it be replaced

1. What is the wear part? Every product has one component that reaches the end of its life first: a gasket, a bearing, a blade, a filter, a switch, a cell, a cord at the strain relief. If you cannot name it, you cannot predict how long the product will last, because you are guessing about the wrong parts.

Then check how that part is held. A gasket in a groove is a two-minute job. The same gasket molded into a housing makes the housing the service part, and the product’s life becomes that assembly’s life.

2. Are spares actually sold, and for how long? A parts diagram is not a supply chain. What matters is a page listing parts with prices and stock, rather than a form asking you to contact support.

Duration is the harder half. No general federal rule requires US spare parts to stay available, though several states have passed right-to-repair laws covering consumer electronics, wheelchairs and farm equipment. EU ecodesign rules do set minimum availability periods, on the order of seven to ten years, for appliances such as washing machines and refrigerators. Where the same model sells on both sides of the Atlantic, that obligation often keeps a parts stream alive for US buyers too.

Can you get inside, and is the consumable standard

3. Is it opened with common tools? Look at how the housing closes. Phillips or Torx screws mean it was designed to come apart. Pentalobe, tri-point and one-way screws mean it was designed to come apart only by the manufacturer. Pop rivets, heat-staked posts, ultrasonic welds and continuous adhesive seams mean it was designed not to come apart at all.

This predicts lifespan more sharply than build quality does. A repair that begins by destroying the housing is one almost nobody performs, so a sealed product has no repairs, only replacements.

4. Is the consumable or fitting proprietary or standard? Standard sizes outlive the company that sold you the product. A 1/4-20 thread, a VESA 100 by 100 pattern, an E26 lamp base, an IEC C13 cord, a 1/2 inch NPT fitting: each has many suppliers, and supply continues after the original maker discontinues the model.

A proprietary cartridge, pod, bag or connector is the opposite. It converts the purchase into a subscription with an end date the seller chooses, and the sticker price stops being the price of ownership.

After the warranty, and who else owns one

5. What happens at the end of the warranty? Warranty length is the manufacturer’s own estimate of its failure distribution. The more revealing question is what service looks like in year six, when nothing is covered.

There are three usual answers: a parts stream you can buy from, an authorized service network, or a replace-only policy. The third, which covers most lifetime guarantees, tells you the product is not designed to be repaired and that your remedy depends on the company still existing. Terms voiding coverage if the case is opened belong here too.

6. Is there a repair community or a published parts diagram? An exploded diagram in the manual is the strongest single signal that the maker expects field service, because publishing one costs nothing except the argument that the product is unserviceable.

Outside the manual, look for third-party sellers listing parts, forum threads about ten-year-old units, and teardown videos. A category with a used-parts market is one where things get kept. Silence about a model sold for a decade usually means nobody kept one long enough to need a part.

The categories that fail all six

Devices with bonded lithium cells fail every question above, and people buy them anyway for good reasons. Phones, earbuds, cordless vacuums and electric toothbrushes have a glued-in wear part, no consumer parts stream, a sealed case, a nonstandard cell, replace-only service, and a repair community that fights the design rather than following it.

Lithium cells lose capacity with cycle count and calendar age whether or not you use them, so this is a clock rather than a maintenance failure. The checklist is not a veto here. It is a correction to the price: if the realistic life is four or five years, compare cost per year, and prefer variants that fail fewer of the six, such as a serviceable cell, a standard charging port, or a published teardown.

What to look for

None of these six questions requires trusting a review, including this one. They are answered by documents the manufacturer publishes and by what other owners have been able to buy. When the answers are missing, the absence is itself the answer.