Nothing lasts forever. Even the good stuff. Furniture takes a beating and it can simply break.
Unfortunately, repairs are often done improperly and not surprisingly fail again in short order.
The usual culprit is failing to clean out the old glue. If someone says they will apply some glue and clamp it up for you it will last for a while, but most likely it is going to fail again because glue needs to hold on to bare fresh wood, not old glue.
If you are going to do the repair yourself, do yourself a favor and clean out the old glue. you can clean it out mechanically with sandpaper, or with vinegar . In any case, it may take some time and effort to clean it out of deep mortises and broken dowels/tenons.
And keep the clamps on for at least 24 hours. The longer the better before you apply stress to the joint.