Can I switch between monthly and annual billing terms later?

Generally, yes — at renewal. When a monthly or annual NCE subscription comes up for renewal, you (or your partner) can typically select a different term for the next cycle based on your current needs.

Switching mid-term (before the current commitment ends) is more limited — annual terms are generally locked in until they expire, aside from adding seats. If your needs have changed significantly mid-term, your options are usually to wait for renewal or discuss alternatives with your partner on a case-by-case basis.