We don’t use much the conversion, so I’m not sure I can give good advise, but it seems logical to not keep the converted file, as it would mean keep twice the same data, just the layout, or even only scheduling group, would differ.
The impact on operation depends much about the number of conversions operated on an instance. If very few, no problem, as the files will be removed from recycle bin after expiration. But when many conversions are done like in group balancing activity, it would fill up the recycle bin, which would cause issue to users removing files, and I suppose also to conversions themselves.
So at least a parameter that could be changed to inore the recycle bin policy for conversions (or only group balancing) would be nice.