An example of a 10+(!) year technology lead is computational discrete topology. Every large-scale geospatial, graph, et al analysis system is based on it — you can’t build one without it — but there is virtually no literature on how it works and a practical expression of the theory is robustly non-obvious. The same few people continue research and design every kernel for companies/governments. AGI and autonomous systems specifically drive much demand for this tech currently, since it is needed to reason about relationships/behaviors in space-time at scale.
There is no company behind this tech currently but I’ve heard rumors of one being created. It could have a strong feedback loop, not just due to tech exclusivity but because a platform-level implementation would effectively provide a consensus model of physical reality for machines.
Tangentially, I am aware of AGI research programs working from first principles that have made impressive theoretical CS advances while completely under the radar. It is difficult to determine if any have 3+ year leads on any other program though since that assessment implies global visibility.
Distinguishing between a technological lead and ineffective competition is also important. An example is database engine technology. Some proprietary databases are orders of magnitude more efficient/scalable than any open source comparable, which looks qualitative, but is widely recognized as a product of design quality rather than any technological lead. (see also: Google’s data infrastructure)