i like 30. I used to think that 24 was the max i would ever go but since I got my 30 deep, its been OK. Tough at time but not impossible. I suggest getting these surgical forceps:
http://www.excelinnovative.com/servl...s--dsh-/Detail
they come in different lengths and are very effective for reaching down to get things from under rocks etc. They are also very strong and durable.