What is the criteria that works out if you get cleared payments on orders immediately, to be paid out the next day, or if they take 24 hours to clear.

Similarly some people have funds held for cases and others dont

As a Top Rated seller with zero defects, I've had 24 hour clearance for a while and funds held for a while, whereas I did not earlier in the year.

What governs this, so I know what to look for?