Whether it's toner, a fuser unit, or any kind of consumable used in digital printing; not having it when you need it is a big problem. We maintain a full warehouse of supplies for all kinds of machines. Hearing that the toner or drum you ordered is on backorder right at the time a big job is due is about as bad as it gets. You can count on MSL.
Using genuine supplies is critical. Many aftermarket or 3rd party supplies are refurbished or refilled with cheap knock-off toner. While the short term savings are tangible, the long term downsides are far more significant. Non factory consumables always void your warranty and using components that aren't engineered for use with the machine is a disaster waiting to happen. Do yourself a favor and stick with factory consumables and toner.