Glass doors seem sturdy and long-lasting, and it is possible to have one for many years. But there are signs that the door must be replaced that you need to pay attention to. Replacing the door can save you money on your energy bills and keep you and your family safe from injury.
When dealing with glass for doors and windows, you have a couple of main types: annealed and tempered. Tempered glass is the type you see in car windshields, where the glass breaks into little bits when broken. The bits can still be dangerous, but you don't have massive, stabworthy shards lying around. Annealed glass, though, breaks into those shards. Not only are those dangerous themselves, but WBBM-TV in Chicago reported in 2014 that if an annealed window already has damage to it (but not enough to make it fully shatter), then merely leaning against the window can cause it to break and injure you. If your door is made of annealed glass (WBBM notes that tempered glass has the manufacturer's name in the corner), replace the door with one with tempered glass.
If the door still uses single-pane glass, you really should replace it with one that has at least dual-pane glass, if not single-pane glass. The extra panes and gaseous interior space help stop temperature leakage during hot and cold weather. The panes also help block out extra noise, too. The single-pane doors may look pretty, but you can get some fashionable dual-pane (and more) doors as well. Plus, some companies will custom design a door for you if you want to make the door fit in with the rest of the house's architecture.
Sometimes it's not the glass that is the problem but the surrounding frame. If you've got a decorative pair of French doors, for example, the wood in the door can develop mildew patches and start to rot over time. If that's happening, it's best to replace the door so that you don't lose energy efficiency or find the door becoming physically weakened. Weak doors are also easier to break through, so this is a security issue as well.
Start checking out door styles now, even if you don't think your current door needs to be replaced yet. If you know what's available -- and glass door manufacturers and sellers can show you catalogs -- then taking action once the door does have to be replaced will be easier.