This is the sweeping advice I was given:

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"frequent sweeping will delay transaction start-up, as the time since
the last sweep increases, the time for transaction startup will also
increase.
this can all be avoided by more frequent back/restore and less frequent
sweeping."

...

"Only if you CAN'T do timely backup/restore operations AND your
application results in large numbers of rolled back transactions, you
should do sweeps, but do not do them frequently."

...

"You can reduce DB peformance significatnly by sweeping too regularly.
You are much better off doing a backup/restore cycle. If you do know
that a seeep is unnecessary then don't do it. (certainly not every
night)
that's my understanding - it's not a matter of belt-and-braces, it's a
retrograde step for overall performance"

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Comments? ;)

John