Aloha a nui loa! From years of repairing and working with printers:
Leaving the printer in sleep mode to run cleaning cycles is not a good idea. Here's why:
You do not want the printer to do these cleaning cycles. The more it does this, the more chance the ink will clog the nozzles. TURN IT OFF at night or when not in use for long periods. Also, by running so many cleaning cycles you run the risk that the printheads will clog up even more than it would if it runs the sleep mode cleaning cycles. You should only do as many as the manual claims (usually 4 or 5) preferably only 3.
Make sure you print color every week or so. The less you print color the more the ink will dry out and clog those nozzles from lack of use.
When the printheads don't get better with cleaning cycles. You might try a Power [Exhaust] Purge in Maintenance mode. When that fails (this can also render printheads useless so only do this ONCE), you can try to manually clean the printheads (since they are permanently installed and only completely disassembling printer will let you fully access them). WARNING - If the pwr surge cleaning works, do not run a regular cleaning cycle because you may completely lose one or more colors. After that, other than a manufacturer repair (UGH too much $$), a manual cleaning is your only hope.