though I am not sure how you have emoncms setup-- could you not do what openwrt does to reduce to utmost minimum ( one reason I like openwrt so much) . everything about the OS that has any form of writes is done on ramdrive - ie - /tmp and /var – the database is persistent… with openwrt at reboot it simply recreates /tmp ( empty) and /var ( rewrites the basic static files required) and other stuff via overlay of non essential data --very little writes to the SD or eMMC ever.
when I set up my kodi box on ubuntu I did the same to it ( or as close as I could). first i installed Zram-config to compress my ram so i have more of it . And since it has relative high volumes of writes to the html folder for weewx numerous files rewritten constantly… recreating the website over and over continuously … I set aside 24 megs of my ram just for websites
tmpfs /var/www/html tmpfs nodev,nosuid,noexec,nodiratime,size=24M 0 0
and whenever my device reboots it simply recreates the website into ram. reducing my SD writes to very very little only the persistent writes to the database . and every thing else is recreated at the next cycle pulling persistent data from database and recreating incidentals ( *.xml *.json , images … etc )