>I'm never going to sit down and review the cards
Well, don't sit down then. Standing up flip through the cards you filled during the day and toss them into garbage, unless one is really important. You're strictly better off than writing down nothing at all during the day, which is the default state for most people.
Later in the day when I pull them out, many do get trashed. Lots of Todo items never make it to my digital Todo list because my brain processed them mostly in the background during the day. I find the physical nature of the cards means I can't avoid that processing step. The times I revert back to digital first, my notes end up everywhere (I input them in the fastest way, rather than finding the right place) and immediately begin rotting because now I have remember and force myself to condense and organize rather than it occurring naturally.