Increasing time out value

There are two timeouts you could be referring to :)

The first is the time between a client connecting and it sending its CONNECT command. This is set to 60 seconds at the moment (although the server only disconnects the client at 60*1.5=90 seconds) and can only be set at compile time - see the line "context->core.keepalive = 60;" in context.c. I doubt this is what you are referring to because it doesn't really relate to data transfer speeds.

The second is the keepalive value set by the client. If the client doesn't communicate with the broker within the period 1.5*keepalive seconds then the broker will disconnect the client. Like I say, this is set by the client and it is the responsibility of the client to ensure that PINGREQ messages are sent to the broker if no other messages have been sent within the keepalive period.

The way you should deal with this depends very much on what you using for your client code. Assuming you're using libmosquitto, this is all handled for you and you just need to use the keepalive parameter in the mosquitto_connect() call to set your keepalive value. I can't comment on other client code because I haven't looked at any - you'd have to check their documentation.