If it's a really inexpensive transaction (for example, from 5 to 20 US dollars, which is not unusual for non-TTL compatible digital equipment) … you buy two and you do not care so much that you can still have a few thousand to a thousand. spring of each. Which is very likely since you can assume that the "few million" above are close to the truth.
It is statistically unlikely that you buy a flash with exactly 1% of tube life.
The main causes of the non-functionality of old used flash guns tend to be poorly maintained battery compartments that have been flooded with battery acid (which can usually be repaired if there has been no migration of the battery. 'acid in electronics proper) and which are worn, aged or poorly maintained. capacitors.
There is a good reason why it is not necessary to assume that the scheme of any Speedlite flash is even close to "60% of the explosion energy": Electrolytic capacitors, such as those used in flash guns, are very loosely tolerated towards the positive (+ 20%). We find the capacity in a datasheet from a well known manufacturer, for its photoflash products (some brands could represent + 50%!). Something designed to be equal to 50% would suddenly be 60% this way from time to time, and would fail very quickly if it was used in full power manual mode.
A branded flash gun only valid for a few hundred cycles would quickly discredit the manufacturer.
If a previous user has used a flash to the point of being subjected to high thermal stresses, it usually appears a discoloration / fusion / … transparent plastic diffuser.