Problem with chaining many small DMX cables
There's a maximum rule of 32 devices and 1800 feet (548m) of cable in a single chain, though generally people seem to aim for about half that number of devices in practice. Each connector you add in will have an impact on the maximum length because of the resistance it adds in.

I doubt that you'll have any problem with multiple extensions unless you're talking about hundreds of metres. Even so, I'd be inclined to go with longer extensions (10m or even 25m) and less of them - there will be fewer connections to fail.