I've actually had similar questions asked of me just recently, but I haven't yet posted those emails to my Questions and Answers forum. Please check back there later, as I'll try to have those answers up within 2-3 days. Hopefully a couple short answers will hold you until then. :)
The number of times you can apply to each medical school varies with the individual school. However, many schools will cap the number of attempts at 3-4, and therefore if this is a concern, you should email each medical school and ask.
In practical terms, *most* people only apply three times, with four as a maximum number of attempts. It costs a fair amount of money, and takes a tremendous deal of time each time you apply, and the average applicant's patience and stamina is usually worn out after several tries. Three or four years is also a long time to put off your life considering that medical school eats up four more years, and most specialty residency training programs take an additional 4-6 years, family medicine notwithstanding.
With that said, we have at least one member of the class who was accepted on the fourth attempt, and numerous members who got in after three tries. The chances of getting in after three years is quite slim (only 8-9 students in my class of 120 got in after three years). You need to have an excellent GPA, a strong MCAT score, and good extra-curricular activites and a positive interview. In other words, it's not easy. :( In order to accomplish this, you'll probably write your MCAT in the summer after second year, which I think is the best time to write it irregardless of when you plan to apply.
I do think applying after third year is a good thing. It gets you familiarized with the application process, forces you to work on those essays and reference letters a year sooner, and heck, you might even get in! :) I believe those positives are well worth the application dollars, although I'm sure others will disagree.
Finally, if you're anything like me, you'll love the "smaller university" atmosphere. Looking back, I loved UVic, and think I would have been quite unhappy going to UBC during undergrad. Despite the strength of UBC's academic reputation.