I would say that the 150 cases are enough. I sometimes shoot pretty often and I am satisfied with the 100 pieces of .308 brass I have (+ another 20 factory loads I'll be keeping around for any serious use).
However! Given the rarity of .445 brass, I probably would recommend getting that extra hundred.
For 9mm I have about 600 or so pieces (though I still collect whenever I can) and for .44mag I only maintained and reloaded 300, though I was shooting .44 out of a revolver and putting about 150 rounds a week downrange, so for a Handi I'd have probably been fine with maybe 100.