Should you extend your base classes in your BC Model project? It's up to you if you think you'll need to. Do you think you'll need to change a built-in feature to behave differently or to add a new feature? Do they need to be used by all of your applications? To do so requires that you do it prior to generating any business components in your project. The most common components extended are:
- Entity Definition
- View Object
- View Row
- Application Module
- Database Transaction Factory
- Database Transaction
doDML()methods handling the transactional commit operation.
So there are a lot of benefits to using extended base classes. It's just up to you and your development team to use it the right way.