If you test all possible combinations before finding a block. Best case, you immediately find it, worst case you find it on the last combination, average, you will find the block in about half the time of the maximum.
But no single miner searches all possible combinations by itself and as far as I know there is no decided range of combinations tested by each pool so different pools may end up testing the same combinations. and different pools include different transactions so operate in a different search space. This means that the upper limit is a lot higher than twice the average block time.
Random results do included things humans don't find random at all. 100 slow blocks in a row is less likely that 10 slow blocks in a row, but not impossible.
The search space is astronomical - we'd be waiting a very long time indeed if there were only one solution. Fortunately, there are many solutions within the space. You can still keep trying unique combinations and miss an answer for a
considerable time though.
There were far too much blocks in the hours before
7,17/h blocks in the last 6 hours
7,42/h blocks in the last 12 hours
https://fork.lol/blocks/timeGambler's fallacy that one, I'm afraid
