There was no television in the silent era, but audiences had a voracious appetite for films, so most studios tried to pump out movies as quickly as possible. However, depending on the year and the studio, films still might be produced quicker or slower than average. For instance, Laurel & Hardy spent about a month working on their silent films, although these were only two-reel (20 minute) comedies.
When Charlie Chaplin got into features, he spent three years each on his The Gold Rush, The Circus and City Lights. He was a perfectionist, and filmed scenes over and over. He scrapped whole scenes that he didn't like after spending days filming them. He also took vacations and put the films on hiatus when he couldn't find comic inspiration.
However, when he worked at Keystone in 1914, he might appear in 2-3 short comedies a month. These were filmed quickly, with barely a scenario and a lot of improvisation. Chaplin was happy when he worked at Mutual in 1916-1917, and he could devote a month or two to a two-reel comedy.
Most of the special effects in silent films (there could be quite a few), were actually done in-camera. The post-production part of filmmaking was editing, tinting (sometimes), preparing alternate negatives for foreign releases, and possibly preparing a score for the film. Only major films had an official music score, and only a few theaters actually used them.
If you look at the end credits of a modern movie, you will notice that there are all kinds of jobs credited like caterers, accountants, lawyers, hairdressers, animators and so on. While these jobs existed in the silent era, modern films and studios have a lot more bureaucracy that takes a lot more time. Also, modern studios are not geared up to produce as many films as quickly as possible these days. That does happen for episodic television though.