e2fsck slows boot

In most cases, Ext3 (other than ext2) should not do a long-winding check when mounting a not clearly unmounted volume, but use it's journaling tables to do a fast recovering to the latest clean transaction.

OTOH, a CF is a great problem when unexpected power fail is possible.

The card needs to do internal wear leveling and thus it maintains tables which sector is stored where in the flash memory, as each flash page (which can be erased only completely) contains thousands of sectors. When a page wear out is detected, data needs to be moved to other flash pages and these tables need to be modified (possible creating additional wear-out conditions). This can happen with any sector write, and unfortunately the time needed for this until all data has been written to the Flash area, usually is not specified by the manufacturer. I suppose it can be some seconds worse case. (Please tell us if you found a CF manufacturer that publishes appropriate numbers !)

I was told about cases showing that this effect destroys very old data and sometimes even destroys the card in a way that all data is lost and it not even can be reformatted. The manufacture can revive it by rewriting the sector tables, though.

IMHO you only can use CF devices for writing data in devices permanently enough powered by a battery.

Using high level means like alternative file systems obviously does not help here.