After collecting US$ thousands for Win 10 Ent/Pro Volume Lisensing, M$ allows enterprises the facility to setup their own KMS server to self-activate their Win 10 Ent Volume Licensing on hundreds or thousands of their computers using ONE common KMS/MAK key. As a condition, M$ only allows this key to be activated for only 18 months = the computers need to be reactivated by the KMS server every 18 months.
Cheap Win 10 keys at about RM5 each sold at shopee or Lazada are often such keys that have been illegally leaked by employees = such keys will only last 18 months before becoming deactivated since the gullible key-buyers' computers are not connected to the particular enterprise's KMS server.
Universities also give such "free" Win 10 Education/Pro Volume Licenses to their students but such licenses have actually been heavily discounted by M$ for universities/colleges. Students may also leak and sell such "illegal" keys cheaply at shopee or Lazada.
In China, India and Russia, pirates setup their own KMS servers to reactivate pirated copies of Win 10 Ent/Pro every 18 months because the governments there condone Windows piracy.
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Is Windows 10 key from Lazada trustworthy?, It's just RM8 per key