My first, and most raw impression of your question is if there is a limit to how many
guns, not just C&R guns. is a personal limit. The answer is of course yes, I reached it about 15 guns ago!
Now in reference to C&R guns, because this was posted under the C&R forum, my personal limit is controlled by what is in the market. I am not a collector of fine antique firearms, but rather a shooter. My C&R collection is made up of reasonably priced, and some times down right cheap milsurp firearms. A bit of hint as to where my username came from.
The milsurp market is not producing much in the way of firearms I don't already have one or more examples of. So as far as C&R is concerned I am probably close to my limit.
When it comes to commercial new and used guns, there's a lot more to help extend me well more than 15 beyond my limit.