Bests & Worsts Reviews from Amazon

I have a Panasonic DMC-LX100 which can record 4K 30p video at a 100Mbps bitrate and sometimes recording would stop with an error saying the card's write speed cannot keep up. This happened with a $28 PNY Elite Performance SDXC 64GB UHS-1 90MB/sec card so I got this Lexar SDXC 128GB 150MB/sec UHS-3 card and it works perfectly for 4K 30p. UHS-1 guarantees a minimum write speed of 10MB/s while UHS-3 has a minimum of 30MB/s which is probably where a UHS-1 card falls down for 4K. I informally tested the Lexar by recording four back to back 15 minute 4K recordings and the LX100 got very warm, but there was not a single hiccup. The Lexar card also recorded 100 12MP still shots in the 11fps high speed burst mode before slowing down. The PNY could manage 95 shots before slowing down so it's not a huge difference for stills, but I wouldn't want to risk using the PNY for video and having a 4K recording stop unexpectedly. In Windows 7 with an OCZ Vertex 4 SSD and Transcend USB 3.0 card reader, I copied a 6.5GB file to and from the Lexar card and it averaged about 60-65MB/s writing TO the card and copying FROM the card averaged 87-90MB/s. Basically, this Lexar Pro card seems to be rock solid for 4K recording and I will update this review if I have any problems. On a side note, it annoys me that even though most cameras format SD cards in exFAT which no longer has a 4GB file limit size like FAT32 did, a 30 minute clip will still be broken up into 6 or so separate 4GB files. I'd like the option to record a video into one giant file. In addition, most cameras limit video recording to 30 minutes due to some EU tax applied to camcorders, but since we're in the US, I don't see why we should be stuck with this limit too. Fortunately, the US version of the upcoming Panasonic DMC-FZ2500 4K camera seems to have no recording duration limit and may even support files of up to 96GB with an SDXC card. I can't wait to see if this is true. UPDATE (09-29-2015) - I uploaded benchmark results with a new card reader Kingston Digital MobileLite G4 USB 3.0 Multi-Function Card Reader (FCR-MLG4) and CrystalDiskMark 5.0.2 x64, Windows 10 Pro. READ (MB/s): 152.7, 14.67, 152.3, 11.52 WRITE (MB/s): 86.69, 1.231, 85.15, 1.180 With tape over extra ports: READ (MB/s): 91.87, 13.18, 92.92, 10.04 WRITE (MB/s): 75.92, 1.134, 75.50, 1.093 UPDATE (11-16-2016) - My card is still going strong and I haven't had any problems. I am looking at new cameras like the Panasonic DMC-FZ2500, Fujifilm X-T2 (two UHS-II card slots!) and the Sony A6500 so I may buy more of these Lexar SDXC cards and make the old reliable one as the backup.