The specified target goal for most of the battery powered sensors which will work with SmartThings is two years, not a few months. It can still be annoying, but it’s not as annoying.
Most people who are using sensors for home automation in this community seem to choose battery powered ones. They have more features, can be placed in more locations, and are a bit simpler to add to your account. (The exception, as @the2352 notes below, is some of the dual purpose mains powered devices, like the newest GE switch which includes a motion sensor. )
However, there’s another group of community members who are using sensors for security purposes and want at least one on every window. Those folks are generally using inexpensive dumb wired sensors and then connecting them to a smart panel, typically using a product called Konnected. This greatly reduces the total cost of the project.
Very few people use a lot of the smart plug-in sensors. Those are generally just used two or three for an account for some very specific use cases.
See the following recent thread for a detailed discussion of all these options (this is a clickable link)