This depends on how much you're farming. If you have one bot going and another account, then you might find it worth your time to go ahead and make flasks etc. But if you have a lot of bots going, it get's tedious sitting there hour on end making flasks, it's just easier, more practical and worth your time to just sell the herbs. I get a 100+ stacks of icethorn/lichbloom/adder/goldclover a day among the stacks of frost lotuses, so it makes little sense for me to sit and make/mill herbs into something else.