Are there discounts for committing to an annual term instead of monthly?

Generally, yes — annual-term NCE subscriptions are typically priced lower per seat than the equivalent monthly-term subscription, since you're committing to a full year rather than being able to adjust or cancel each month.

The tradeoff is reduced flexibility: you generally can't reduce seat count or cancel an annual term early without penalty, whereas monthly terms let you adjust more freely at a higher per-seat cost. Which makes sense depends on how stable your user count is expected to be over the coming year.