How many printers would necessitate a separate print server?

This would basically depend on your financial situation. First of all the printers would have to be able to hook to a drop with a network cable & you would have to configure the price per drop.

If the printers are all on the same subnet or building I would say yes...if not, I'd say no.

Would there be any benefit to moving the print server to a separate physical server dedicated just for that if i have a spare server?

Processor process one task at a time, with high processing speed you will think that processor processing 2 or more tasks at the same time.

Now, do you feel that the current working printers have latency in printing pages?
if yes then use your spare server.If no then just let if be.

What roles does your current print server run? If it's running low resource roles at present anyway, you would gain virtually no benefit of moving the printing to a dedicated server.

Domain Controllers and File Servers are typical examples of servers where you could easily run a print server without having an adverse effect on any of the roles on the server. However, if your current print server runs SQL Server, Exchange or anything particularly intensive on the system, then moving the print server to a less worked or a dedicated machine would be a good plan.

Let me know,

-Matt

The current server currently has a load of different tasks, so there's no question about the fact that it has to be moved off to a different server.
My question is really more hypothetical than anything.
I was just interested how the "big guys" do it, how may printers would you have to have for it to require a separate machine.
just like they sometimes put AD on a different server, but only in big companies, not in smaller ones.

sorry if this is confusing.

p.s. All the printers i have are networkable.

In large orgs you'll usually have centralized print servers with hundreds and hundreds of printers on them. Properly configured a Windows print server can support a massive number of queues. You see the service collocated in branch office situations where you are serving a small number of users and it's not economically feasible to split the roles onto seperate servers.

Thanks,
Brian Desmond
Active Directory MVP