It is safe to stay with 2.3. That said, we are no longer developing that branch, and you will miss out on any new features or bug fixes. If it works for you, and you can deal without the new features, stick with 2.3.
Even if you didn't usually have issues upgrading, I would highly recommend doing frequent database backups. This way you're not stuck with lost data should you decide to finally upgrade and there is a problem.