They absolutely take the forces of recoil for many tens of thousands of rounds. One not uncommon problem, however, is loosening screws. You can't blame the red dot sight's durability for improperly torqued screws, screws installed without anaerobic threadlocker (Loctite), and for very thin slides that don't allow much screw thread engagement. Provided the installation is good, the sight itself will survive shooting.
As was mentioned before me, not all red dots survive drops. They are glass. The RMR has the best reputation for drop survival, but it also has one of the smallest windows. Some factors that affect drop survival are the weight of the pistol, the surface it lands on, and its orientation when it lands. The sights are not delicate. People routinely use them to violently rack the slide, even against walls and door frames and such (one-handed racking). But the glass can crack if the shock of a drop is too much.
A cracked window does not render the gun unusable. In fact, any kind of red dot sight failure is just that -- a failure of the sights, not the gun. People bend and break iron sights dropping their guns too. You can still hit what you point the gun at, and you can even still aim the gun using an alternative index. This is why "back-up iron sights" (BUIS) are over-rated. You don't really need BUIS to keep the gun functioning. You just need to improvise. What's more, BUIS clutter the sight picture and potentially slow dot-acquisition.
There are other disablers of red dot sights. The window can be occluded with dirt, mud, snow, blood or whatever. It can be occluded in the front so the reflection of the dot is still visible, or on the back so the dot is not visible. The LED emitter can also be occluded so that there is just no dot in the window (this is less likely with enclosed emitters such as Aimpoint Acro or the tube-type that aren't popular for slide-ride, at the expense of bulk). Batteries can also fail, though I think that is over-fretted. Again, iron sights aren't necessarily usable if the gun is caked with mud, snow or ice, so these kind of "what if" scenarios don't destroy the proposition of red dot sights. Train with occlusions by taping the sight front, taping it backside, and taping over the emitter. Practice an alternative sight index like marks, grooves, or edges on the slide, and practice point-shooting. The idea that you'll be better off with only iron sights instead of a red dot because all this unlikely stuff can happen is just far-fetched and irrational. Hunters and warfighters have been comfortable with the liabilities of optics for a long time and aren't about to go back to irons-only because of some kind of imagined superior reliability for critical applications.
Red dot sights (miniature reflex sights to be more specific) are even better for revolvers. Right now the shortcoming is that they're all designed to sit on a flat slide top, so the installation on a revolver is usually via an flat-plate adapter. That part is kind of lame. But the red dot on a revolver doesn't reciprocate -- semiautomatic pistols also have the option of frame-mounted red dots at the cost of bulkier mounts. In my personal experience, the red dot on a revolver gives up nothing compared to adjustable "iron" sights (factory S&W, which are actually plastic and steel). I never considered the factory sights "durable" and anyone who uses a fiber-optic front sight certainly has something less durable than a good red dot. So while giving nothing up, the red dot is a great aide to older eyes with presbyopia and it is far superior for precise aiming at more distant targets (50 yards and beyond) -- this is especially so with smaller dots like 2.5 or 1 MOA, probably not so with 6 MOA dots.
