I have always used sables and later kolinskys for my miniatures work. But at the end of the day they are consumable items. I have found that painting metal seems to wear brushes at a speed that people who work on watercolour paper (what most sables etc are designed to be used on) wouldn't believe. Used only for watercolours, a good sable will almost last a lifetime. Even on plastic kits with enamels back in the day they would last for years. On minis, they last a few months. And that's with not using them for drybrushing, inking or mixing - I use old brushes or synthetic mixes for these parts of the process.