NAF stablehands is good for regular use - I have some in my car - although I find the lemony scent rather overpowering....
I find L'Occitane do the best hand cream - it's similar to the Body Shop Hemp one but smells far better and lasts longer. Is quite expensive but a tube lasts me forever as it's so intensive. That with the gloves overnight and hands are sorted.
I think frequency of application is the major factor - I apply hand cream every time i wash my hands and normally have very strong nails and soft hands.
It comes in a round blue tub (about 200mls) and costs about £3-4. It is quite greasy so is probably best used overnight with some socks or cotton gloves on your hands. My hands haven't split at all since I've been using this twice a day.
I'd also recomend putting germolene cream on the splits to help heal them
Another vote for the body shop hemp cream. Sorts my hands out in a couple of days of using it several times a day. I then only use it every few weeks til they go bad again.