Using a SSD or USB memory for backup while travelling would not bother me so much as long as I didn't delete anything from the SD card in the camera, so I have 2 copies at least.I have 2 RAID backups of enterprise drives for security and reliability, and would use the SSD version for traveling, as they are so lightweight. I buy high quality Samsung or Sandisk SSD's and have not had any problem, nor have I every had a SanDIsk SD card go bad and I probably have over 25. The only Lexar and Transcend SD cards I bought did have problems though.
Right now I am using the Oyen Digital MiniPro RAID with 2 of the WD 5TB drives for my mobile setup. The 4TB version of Segate 2.5" drives only lasted for 18 months until my DriveDX app said they were past recommended maximum life.
But for long term backup I prefer HDDs.
I usually have my laptop PC with me while travelling and then I even backup to the cloud as I go, 1 copy on the SD card, 1 copy on the PC HDD and 1 copy in the cloud.
I might be paranoid, but am I paranoid enough? Obviously not as I still have lost files, but at home where I am not that diligent.