I know BNC barrel connectors cause signal attenuation(weakening of the signal),which I imagine could affect the transmission speed and quality due to the recieving server having a hard time reading the signal,and possible need for retransmission of the signal.It's always best,whenever possible,to go with one solid piece of coax.If this is not avoidable,and you have to use a long cable with a number of connectors,I'd recommend a repeater.

Also,if such an arrangement is necessary,it sounds like your network may be a little too big for the particular physical topology you're using.For example if you are using a bus topology,you might want to consider a star or star-bus,that way you can make more effecient use of the shorter pieces of cable.Or you might want to implement a thicknet to thinnet structureto reduce signal attenuation and increase range.

There's a million different ways to solve such networking problems.If I were you,I'd get a Networking essentials book or something along those lines and learn the stuff yourself,because along with the different physical and logical topologies,cabeling types,and different connectors,repeaters,hubs,and routers,you have a budget and that is going to be the main obstacle in most networks.