If you're playing in a key with several flats, and you don't need to go above first position, is it better to go into half position so that you're not constantly reaching back with the first finger? Or should you reserve half position for those cases where the second finger needs to be a semitone above the first, eg B flat and B natural on the A string?

I know I can ask my teacher - and I have - but I've been told different things by different teachers. I'd like to know whether there's a consensus.

If I'm playing in something like C minor, or Ab, then I do tend to base my left hand further back. There is nothing wrong in reaching back with the first finger, but if most of a piece can be played in first position and has several flats, it just makes more sense to 'stay back' and keep the hand position in a relaxed natural position.

If a piece has several sharps however, I will often base my hand on the placing of the fourth finger and reach back with the first. This is a particularly useful skill for those with smaller hands.