Like i said above, roughly 15-18 hours
Doesnt matter, the FAT32 file system on usb only allows 4gb files max, and since 4gb drives arent really ever 4gb, usualy 3.7gb or 3.8gb, u can either get a 4gb usb and id do it is 2.2gb splits, then only two isos parts, or get an 8gb and do it in 3.8gb...