It's less of cheating and more of toner is not heavy enough to maintain the desired darkness (it's a passive toner system, the toner uses its own weight to print). It's honestly wasteful but unfortunately active toner systems costs more and is much heavier than the already-heavy passive toner systems.
Sounds like you could remove the leftover toner from the first canister and add it to a second one after some use, reducing waste and not having the darkness issues.
But they're not refillable, you might say. Usually they're thinwalled plastic, nothing a little knife and some duct tape can't solve.
> Sounds like you could remove the leftover toner from the first canister
I am big on antiwaste, but if you have ever accidentally released toner, you realize that it's a very fine powder that aerosolizes easily and stains everything it touches.
