I cannot emphasize more the importance of setting the correct layer break point for dual layer DVDs, the so called DVD-9.
Most software, including the famous ones such as DVD Studio Pro and Encore sometimes set the layer break point at the wrong place. But your question is: It works though. Yes, it may work on your DVD player but may not work on other players. There is a very funny phenomenon in the DVD player market; i.e. the cheaper the DVD player, the more compatible it is. Why? Because cheap DVD players are created to play the cheap bootleg discs and if the requirement is too tight they may fail to play. On the other hand, brand name players such as Pioneer, Sony, Philips, etc. confirm to the DVD forum standard so they will reject bad discs, including dual layer discs with a bad break point.
When you have a dual-layer order please make sure to hire a company that knows how to set the correct layer break point. If the layer break point is set incorrectly a knowledgeable replicator such as New Cyberian should be able to fix it without the need for re-authoring.