Well, @rovster (above) is recommending 80C in an oven. He gives no reference for that number, but maybe that’s the threshold to look for in a PEG filament dryer.
The idea of using the X1C as a filament dryer is an interesting one. After all, it does have both an exhaust fan and an internal fan for circulating the air around like a convection oven. Would it need a stand or something to lay on so that the heated bed doesn’t melt the spool by direct contact?
Stefan at CNC Kitchen did some testing and found that PETG could become unacceptably moist in as little as 6 hours in unprotected atmosphere. As @T_guttata points out, some prints require much longer than that, so therefore some kind of external filament dryer that’s “always on” seems warranted, unless maybe desiccant alone is enough to keep a spool dry after you’ve dried it out with heat.
Regardless, you’ll know in much less than 6 hours whether or not wet filament was the cause of the botched prints.