According to this question: Where can I find the default timeout settings for all browsers? each every browser has a default setting for time out
The default timeout in Firefox17, after checking about:config is 115s. However I have tested to run some request in which I timed and it returned a request after >150~ seconds.
So I wonder how does it works, shouldn't Firefox have timed out before?
According to https://bugzilla.mozilla.org/show_bug.cgi?id=592284, the pref network.http.connection-retry-timeout controls the amount of time in ms (Milliseconds !) to wait for success on the initial connection before beginning the second one. Setting it to 0 disables the parallel connection.
go to the url about:config and paste each line:
network.http.keep-alive.timeout;10
network.http.connection-retry-timeout;10
network.http.pipelining.read-timeout;5
network.http.connection-timeout;10
There's many forms of timeout, are you after the connection timeout, request timeout or time to live (time before TCP connection stops).
The default TimeToLive on Firefox is 115s (network.http.keep-alive.timeout)
The default connection timeout on Firefox is 250s (network.http.connection-retry-timeout)
The default request timeout for Firefox is 30s (network.http.pipelining.read-timeout).
The time it takes to do an HttpRequest depends on if a connection has been made this has to be within 250s which I'm guessing you're not after. You're probably after the request timeout which I think is 30,000ms (30s) so to conclude I'd say it's timing out with a connection time out that's why you got a response back after ~150s though I haven't really tested this.
Source: Stackoverflow.com