Often.
For nearly 20 years I ran Rolemaster, which has plenty of published scenarios and settings, but not as much as D&D.
At the moment I run 4e, which has plenty of published scenarios but a lot of them not very good.
As a GM, I think I'm OK at "big picture" stuff, and at interesting resolutions to situations. But I'm very happy to loot the details. I tend to use maps, situations/encounter outlines, NPCs names and relationships, etc. But I like to combine bits and pieces of these together from multiple modules, and/or with elements of my own creation, generally to make the scenario longer and more "epic" than it was in original published form.
At the moment, for example, my 4e game is taking place simultaneously in Night's Dark Terror (a B/X module), Speaker in Dreams (a 3E module), Heathen (a 4e module, reworked and relevelled by me) and has elements of Wonders out of Time (a d20 module) and Thunderspire Labyrinth (a 4e module, reworked and relevelled by me) informing it too. At some stage in the near(-ish) future the PCs are likely to go to the Feywild, where I want to run a conversion of the HeroWars scenario Demon of the Red Grove.