sorry... i should have been more clear. there's 3-4 month slow release, 5-6 month slow release and 8-9 month slow release formulas. i suspect the release should be somewhat close to what the package claims, yet slightly accelerated due to the fact we're actually using it directly in water as opposed to a moist soil where i'd think it would degrade/release closer to those approximations. the (gel?) encapsulate seems pretty resilient, so i'd assume probably within a month of the minimum approximations per each formulation should do well for re-application. so... 2-3 months for the 3-4 month formula, 4-5 months for the 5-6 month formula, etc..
of course this depends on application as well. higher temps will increase the release rate. larger, hungrier plants will demand more feed at the roots, so may be able to fed a little more often to keep a steadier supply, etc.. it's all relative. you certainly could use less if say your substrate is only 1/3 planted, you'd only dose 1/3 of the substrate, etc.. all heavy root feeders? do 7-8 tabs per sq. ft. or 3-4 twice as often, etc..
if you do fertcicles with 4-5/8-9 granules, maybe fert monthly as this is a significantly reduced dosage in comparison. each "00" capsule holds maybe 30-60 granules i'd guess (i'm not individually counting them, lol). low light, no co2? just put one under every rooted plant, maybe two, etc.. depending on excel? can do 5-6 per sq. ft. and water column dosing would be less necessary or wait it out until you see signs of deficiency/get a feel for it/monitor your fert levels through testing, etc..