Singletons are fine if your services/business objects do not contain state and do not require synchronization.
If you need to maintain state in your service or business object, than probably you need to use multiple instances of an object.
Make sure you clearly separate stateless services and stateful business objects in your application. This will make your decisions more obvious.
Also try to avoid lazy loading if possible because it typically requires synchronization which in turn results in performance loss.
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