Question: We have 7 Dlink DGS-3120 48 ports Gig switches stacking together and all ports are being used. Each switch represents a single segment of our working area. it is working well without any issue.

My question is that there is a 5-4-3 rule for network topology, but looks like our switch stack got nothing to do with this rule....? or newer technology has overcame the 5-4-3 limitation?

any idea why?

another question is how many switches can be connected in series?

Answer: 
The 5-4-3 rule is largely outdated: A switched Ethernet network should be exempt from the 5-4-3 rule because each switch has a buffer to temporarily store data and all nodes can access a switched Ethernet LAN simultaneously. More on the [5-4-3 rule here](http://www.webopedia.com/TERM/5/5_4_3_rule.html).
I asked a CCIE the same question, about how many switches can you have in series. He said no real limit, you could string a hundred together end-to-end, for example. There would be some limit depending on the timeouts used by your network stack, but that would vary according to the user.