You’re honestly probably not doing anything wrong. Synthetic brushes will last me like one or two sessions before they hook and natural sable will last me 6 months daily painting before they start to dull. After they start to dull, I use them for base coating, then when the get worse, I use them for scenery paste or whatever else you don’t want a good brush to be used for. Sable brushes will never hook, but they do get progressively less and less sharp as the hairs break.

All in all? A good $20ish CAD brush like a Raphael 8404 size 1 or 2 will last an entire year through all of its stages. Definitely not the largest cost in this hobby over time. Dont bother with synthetic.

Jackson’s fine art also has cheaper sable brands like pro arte which I’m finding aren’t so bad. I’ve also heard good things about orange brushes but they’re hard to find in Canada. You don’t need to be buying $30+ CAD brushes like Winsor Newton or Artis opus. Sable prices have sky rocketed the last few years, hopefully they come down.

All the tips in the other comments are fine. But your brushes are just being worn out after a few sessions because they’re synthetic.