Well Charlie
I can own up to breaking a shaft more than once on my old Stanley stainless steel spade, the fault was actually the shaft made from a plastic intrusion moulding, plus the fact of digging in coal measure soils of Sheffield (all heavy clay)
The remedy I have now is an old Elwell spade, which when I got it came from an auction at Shaftsbury. I took one look at it, has it has steel grips for digging (saves the soul on your boots when digging) First thing I did was get a file and sharpened the working end, you only need to do that once, then it will always stay sharp. The only other thing needed to keep the spade in tip top condition is not to allow anyone else near it!
When I first was shown how to dig in my apprenticeship days, they also issued me with clogs! Which I still have!
Kind regards
Big Ears