The ideal setup for development work is to use both Trivial File Transfer Protocol (TFTP) and Network File System (NFS) servers in your host system and to only store the U-Boot bootloader in either the internal flash or a microSD card. With this setup, the bootloader will fetch the Linux kernel from the TFTP server and the kernel will mount the root filesystem from the NFS server. Changes to either the kernel or the root filesystem are available without the need to reprogram. Only bootloader development work would need you to reprogram the physical media.