HP-41 END vs RTN

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One thing that I have never been 100% clear on with this calculator is when is it better, or more appropriate, to use END or RTN at the end of each program? I don't have a card reader so saving programs to cards is not an option. In that case, I can see the logic in grouping together programs by using RTN and only one END at the "end".

But generally, does anybody have any opinion regarding the relative merits of RTN vs END?

BTW - On my DM42 I always use RTN because then I can save all the programs as a single file.