Monopoly and component limits
Keeping 4 houses on your property(ies) is a very simple strategy that reduces the length of the game quite dramatically. Tying up 8 or 12 houses prevents other players from buying those houses, keeping rents on their properties low, while increasing rents on your own. On many properties, the difference in rent between 4 houses and a hotel is relatively small and is quite easily offset by the lower rents you'll pay when landing on your opponents' properties. The moment you buy a hotel, though, those 4 (or 8, or 12) houses immediately become available for somebody else to buy.

In addition, if your opponent does buy hotels and is later forced to sell them to pay a debt, using all houses on your own property could force them to tear down all improvements. See this question for further explanation. This costs them more money to build back up and lowers the amounts you pay in the meantime.

Using the "unlimited houses/hotels" house rule is probably the number one mistake people make when trying to play a short game. Computer games against AI can be played in 15-30 minutes using the correct rules; 4 player human games will take a bit longer due to thinking time and socializing, but should stay well within an hour. Hours-long games are almost entirely due to house rules preventing people from losing money as quickly as they otherwise would.