I have been running Linux Mint Mate from a Persistent, 32Gb Sandisk Ultra USB 3.0 drive since July without any major problems.
I used UUI to create it. The secret with it to get a persistent drive over the default 4Gb maximum is to first format it as an NTFS drive. If you use the UUI default, it is formatted as FAT32, which has a maximum size limit of 4Gb for persistence.
It will take a very long time to create this persistent drive. I believe it was 1-2 hours, if my memory serves me correctly. The option to use more than 4Gbs persistence only shows up if you pre-format the drive as NTFS. I did this in the standard window drive formatting tool, before i launced UUI.
One very important note, when selecting the maximum size that you want the persistent drive in UUI, is to allow enough free space for the Linux ISO file to be copied by UUI to the drive or the drive will not boot, as the ISO will not be copied to the USB drive.
UUI will give you no warning that the copy failed when the free space is inadequate. That happened on my first attempt.
You can view the USB drive to see if the copy process happened, in which case you will see the Linux.ISO file on the drive.
In my case, the linuxmint-18.1-mate-64bit.iso is ~1.9Gbs and when I view the current isodevice folder in my current file system, it is ~2.5Gbs in size. my casper-rw drive shows as 26.2Gbs.
I may have had more room to make it larger than the 26.2, on the 32GB drive, but I was playing it safe the second time trying to create it,because, as I stated previously creation takes a very, very long time.
Updates work fine and I am now on the latest 18.3, but the drive still boots from the 18.1 ISO.
To actually boot from a newer ISO and update the kernel etc, one would need to create it again. I have not encountered any issues running both 18.2 and now 18.3 with the 18.1 boot ISO. I udate it with the built in Update Manager.
The only issue I really have is running out of free space on the drive. I would therefore recommend using a 64Gb or 128Gb drive to start out with. My guess i though,is that the creation time will be multiplied?
I use this a my daily driver now and only boot back into Windows 7 when I need to. I eventually plan on installing on a real hard drive or SSD, in the future.
I am typing from it now.
Finally, make sure you use a reasonably fast USB thumb drive. My computer is old and only has USB 2.0 ports, But I am using the Sandisk Ultra 3.0 drive, which I believe has faster memory in it. You can, of course purchase much faster drives, which cost more.
UPDATE: one thing I forot to point out is that theoretically, if you use NTFS on a USB stick vs FAT32 the drive will fail sooner because of the constant writes to the file system.
Hopefully someone with more knowledge than me can either confirm or deny this. This was something I had read many years ago when USB thumb drives weren't as reliable as they are today.
Another thing I forgot to mention is that I am doing this on a ~2009, legacy bios system.
This may or may not work on modern UEFI bios system unless your UEFI bios also has an options in it's setup for legacy bios mode. I do know Linux Mint supports UEFI, but I'm not sure if UEFI booting is supported by it for NTFS drives. Maybe someone more knowledgeable will answer that, also.
This link may be of use:
https://superuser.com/questions/588080/ ... ntfs-drive