Really?? Yikes!! My Osmocote package says it lasts for 3 months. Now that's not exact because here in FL it lasts less than that so I re-apply it every 2 months through summer in outdoor potted plants. But I think putting on a timed-release fert every two weeks is going to cause your plants grief once the doses start overlapping. This year I used Dynamite, a fertilizer formulated specially for Florida (high humidity, hot) conditions and it's supposed to last 9 months which means I only have to put it on in the spring, once a year.
Anna, on the Epsom Salts I can't find the article again but I'll post the link when I do. It says that foliar spraying is more effective on most plants because other minerals such a phosphorus in soil or other fertilizers can 'bind' up the magnesium in the Epsom salts making it not as easily available to the plant through the soil. I've been spraying it on my orchids for quite a while but now I just mix up another sprayer and do all the Brugs and tomatoes and other things (anything standing in my way, right?) as well. At least once a month, more often if we've had heavy rain.