Are thermal labels durable enough for shipping?

For standard parcel shipping the consensus across the seller subreddits in our data (r/Flipping, r/EtsySellers, r/eBaySellerAdvice) is that direct-thermal 4x6 labels hold up fine in transit. The known caveat is that thermal labels fade in direct sunlight or prolonged heat, so they're not appropriate for long-term outdoor labeling.