Can I do another border run after using two in the same calendar year?

Hello everyone! My son and I no longer have our work and student visas and after returning from a 6 week vacation elsewhere, we have been on a tourist visa instead. Im not here for long this time, I was hoping to just do a simple border run to extend the 30 days just for this go-around. However, I used 2 border-runs last year before I had obtained my work visa. The last border run was April 2017. I know you can only do 2 border runs "in a calendar year," so I am hoping Im okay to do it again next week. Am I understanding this correctly, or do I need to wait a whole year after my original border-runs?😅