Talking about "perpetual investment funds" for insurance float totally ignores the regulatory constraints that govern these funds.
Float is a potential liability, not free capital, and its availability is closely tied to solvency requirements.
In the UK, the Prudential Regulation Authority (PRA) imposes strict frameworks like Solvency II, requiring adequate capital reserves, making the concept of perpetuity difficult to sustain.
For example, an insurance company that does not meet minimum coverage ratios may be restricted from investing, significantly limiting its ability to use float for potential returns, far from a "low-cost" source.