Yup. That "big bucket", as I call it, holds quite a bit of nutes and that makes it easy to go a few weeks between res swaps.
The plants do exude chemicals as well as take them in. With the bigger res, there's more water to dilute the exudates.
I've attached a couple of PDF's on res maintenance. Bugbee is informative, the CannaStats is more of a "how to" but the Bugbee paper explains why adding back nutes can cause issues.
The biggest thing for me was getting my head around the idea that it's OK to let EC drop from, for example, 1.6 to 1.0 (typical values for flower). I had always thought that the res should be close to 800/500 (PPM) but even at 500/550, there's still a hell of a lot of chemicals in the res…and the rest of them are in the plants.