Numerous different funds, analysts, brokers (and even...

Numerous different funds, analysts, brokers (and even disciplined high net worth investors) have various threshold criteria based on CAP and being listed on ASX200, ASX300, ASX500 etc.

$100 million Market Cap is one such threshold.

Note: very few automatically invest once the threshold has been exceeded (as you say, for a specified period of time). It's more a case of they ignore any stocks that don't meet the threshold.

An interesting one is index funds which do automatically invest. For example, those funds that spread their investment across all ASX200 companies. When S&P re-calibrates their ASX200 list, these funds automatically step-up and buy at market any new members and dispose of any companies that have fallen-off the list.

IMO
DYOR