your answer is confusing and mixing information. It is still unclear in which process step you think it is slow. there is no package size for conversion (step 11), package size is available for IDOC posting (step 14).
started on Friday and finished Saturday morning, this is just unspecific information.
this can mean everything from Friday morning at 00:01 to Friday night at 23:59
I gave you a house number with 13650 per hour, what is your number per hour?
there are numerous other factors that can influence the performance, like the machine size, other mass updates, huge number of users active, and maybe a hundred other things
How often do you post your 270000? Is it a time critical activity? I mean you usually load ahead of a go-live. Anything which is not loaded directly before go-live like inventory, is not really time critical.
And what alternatives do you really have? The batch input method?
how long would you need to create a new LSMW with batch input method? probably longer than difference between IDOC time and batch input processing time(I even expect the batch input to be the slower).