Without actually knowing what someone is doing for that 8 hours we know nothing about X1's stability.
Short of installing live video cam feeds, you're going to have to take comments at face value.
I've done numerous (long - as in many hours) recording/editing sessions using X1... without any problems.
The productions have been pretty straight ahead pop/rock/blues tunes. Some using soft-synths... others strickly audio...
In one case, we were doing pre-production for a tribute band. In this scenario, we'd layout the original tune, map the tempo to the original tune (sometimes involving many tempo changes), then overdub parts the band wants to "fly in" at gigs.
The scope of these projects has been in the 32-48-track range.
Nothing super complex... and no 200+ track epics
Like guitartrek mentioned...
In the process of recording (many fast takes/punch-ins... where the transport is being 'slammed'), X1 was rock-solid. Same for the editing process (comping tracks, cross-fades, fades, slip-editing tops/tails, etc). TBH, I thought that working with many tempo changes might cause problems in X1. Lucky for me, that wasn't the case. We were able to lock X1's tempo to existing audio tracks (sometimes tedious - but tight end results)... and X1 didn't bulk.
For me... (working at a 64-sample ASIO buffer size)
X1 has been solid for what I'd call "straight up" recording/editing/mixing.
Granted, I don't typically use the Step Sequencer, Vvocal, or AudioSnap.
I can shoot iPhone video as proof... but I'd rather not waste the time/effort.