It seems like everything is a subscription these days. We’ve replaced our towers of DVDs and CDs with subscriptions to Netflix and Spotify. The books that used to be piled on our shelves are now bits on a Kindle. In some respects, this is super convenient. Want to bring several books on vacation? It takes almost no space in your bag. Want to switch what music you’re listening to while you drive? Talk to your phone instead of flipping through a huge binder of CDs. Convenient and safe!

Of course, there’s a downside, too. When you have a subscription, you don’t truly own what you’re paying for. Amazon might decide to remove a book from your Kindle. Studios frequently pull their content off of Netflix to put them on their own services. If you stop paying Adobe, you can’t keep using Photoshop.

Some people are pushing back. Jose Gilgado’s “The beauty of finished software” is a great example of the thought. ONCE from 37Signals is a practical example. But people still want bug fixes, and those cost money to produce.

I’ve come to realize that the lack of subscription is sometimes a red flag. A product that charges once for a lifetime of service is a recipe for failure. For example, I bought some toothbrush sensors for my kids. I can look on the app and see how well they brushed. But you buy the hardware and get the app and ongoing service for free. That’s not sustainable. So at any moment, the company might go out of business and suddenly the devices are useless. Of course, one solution is to have a platform that doesn’t require a remote server.

In general, I’m now cautious of buying things that have perpetual service and one-time payment. Subscriptions can be abused, sure, but sometimes it’s the right model or a sustainable business. Of course, I’m also buying movies I love on DVD to put them on my local server.