I'm a beginner knitter. I have a one pair of knitting needles, which are 4.5mm but seem quite short (30cm or less ish? I cannot see a printed measurement for length on them only the diameter). I went to my local craft shop, and they had a great range of needles of all diameters and lengths.
For a new project I need a pair of 4mm however - so what length should they be? Is longer better and just use less of the needle, or should I get two sets of certain diameters so that I can work small and larger projects?