As frequently as you can. I make a LOT of compost and everywhere I can. I could use 10x as much. I trench compost in beds, sheet compost in same, have about 80 gallons in barrels of mushroom compost, and have four bins that get fed constantly. I apply the bins once a year to the beds. But I'm applying directly to beds every week. I get a lot of eggshells (about 15 cases of 15 dozen eggs a week), coffee (about 5 gallons of spent grounds a day), and kombucha spent leaves and SCOBY. I use roughly 300 paper leaf bags full of leaves a year. Woody stems usually sit hidden in at the bottom of compost bins for a few years, buried in bins, or hidden behind plants.
Basically, I don't feel like you can have to much organic matter. Neither does the organismic community my soil.
