2 separate stops in China, can I use 144hr Transit Visa?

Can I arrive in Shanghai, stay for 2 days, depart for another country, then 2 weeks later arrive in Beijing and leave 3 days later for another country? Would these be 2 separate 144 transit without Visa applications and is that ok?
If not, can I use Shanghai as a stopover twice on separate trips spaced 2 weeks apart? We are Canadians Thank you