Say let's say there is a girl from a slavic country. She wants to visit a guy in Canada to stay with him for a few months. So she applies for a tourist visa, not mentioning anything about her guy since a single girl from a slavic country going to visit a boyfriend is a big red flag for her not returning. So instead she opts for a solo tourist visa and she gives meticulous details about her visit, and by some miracle she gets a 6-month visa (even though her intended period of stay is only 2 weeks for sightseeing). So she buys a return plane ticket for the "2 weeks". The hotel was already booked during the visa application time to satisfy the officers. Upon arriving in Canada she tells the entry officer her plans to see the sites, etc and she is allowed entry with her 6-month visa. So next she cancels her hotel since she can stay with her guy and also changes the return date on the plane ticket to 6 months later. So she then ends up staying with her guy for 6 months instead of the intended 2 week tourism on which she applied for. How could the visa officers prevent this?