In my role at my place of work I get drawings from multiple sources that I have to take in and standardize to our format. Sometimes that includes swapping out blocks from the received file to our blocks. In more cases than not, the blocks are in the right place but just need to be brought to our standards. In these circumstances I redefine the block to make it my own with the block editor. If I need to add attributed text to the block, I add it in the block editor and once I have closed and saved the block, I execute the Attsync command and use the Select option to select the redefined block. This results in having the attributed text appear in all instances of the block in the subject drawing.
Notes from Cadalyst tip reviewer R.K. McSwain: Levi pretty much explains how and when to use the Attsync command. If you do not deal with attributes very often you may not be aware of Attsync and another block/attribute command named Battman. Both of these are important and useful tools. See also, related tip #3983.