i have once in a while, but only to make sure there aren't any weird flavors. i don't do it because i like the taste though, uncarbonated green beer always tastes like ass to me.
I taste every time I pull a sample to use with the hydrometer, transfer from something to something else.
( I say every time, but have only made two batches and one in bottles)
all the time....just make sure it is going good. Brown ales generally are not very good green though....much better after about 3 weeks in the bottle. Usually make pale and amber ales.