I want to say that it should only be used after profiling and determining that it's a major cause off GC pressure, however I think there are other times when it

I want to say that it should only be used after profiling and determining that it's a major cause off GC pressure, however I think there are other times when it's obvious that a private scratch buffer would be appropriate. For example, when marshaling an object before writing it to a file, makes sense to write it to a scratch buffer before writing it to the file. It's generally on the order of trivial to keep said buffer encapsulated to prevent any caller from dealing with potential pitfalls. Having clear ownership of the buffer is a big benefit to help reduce any potential issues. You're correct that as a GC approaches perfect, there ceases to be a need for it.