As Judas said, modern CF Cards are more intelligent. Theroretically there is a limit of several 100.000 write accesses per cell. So after ten year of regular usage as harddisk replacement you might put it into trashcan. But normal harddisks mostly don't live any longer.

When I got my Peg more than three years ago I tried to start to use a CF-Card as HD replacement for the first time. But it didn't work for me.
While Linux/PPC and AmigaOS Classic seem to work with most CF->IDE-Adapters MOS seems to be very specific. I couldn't find an CD-Adapter/CF Combo that is recognized by MOS at all and is available in the Union.
There are several threads at MZ already with this topic.

Maybe Acill could tell us, which CF-Adapter and which CF-Card he uses ?