Someone asked me today if it mattered if they ended the semester with fewer than 3 Tokens. I gave everyone three at the beginning of the semester, so this student wondered if it would count against the grade to use them all.
You can end the semester with zero Tokens. Use as many as you need.
You also can earn more Tokens with Excellent work or by attending events. Let me know if there is an online lecture or exhibit that you think should count for Tokens!