I don't know anyone who traveled for so long, but I can help you a bit.
2)
If I do not return to Canada for years do I file taxes? What if I am gone but return for a funeral or something for a few days? What if my bank account is Canadian and my pay is deposited directly into it, will that mean I need to file taxes in Canada? You will be working free-lance throughout your travel? Unless you want to keep your activities under the table, you'll need to produce the yearly tax report. I mean each year, otherwise you'll be penalized. You won't have to pay much tax though, because you are not spending your money in Canada. Sorry to say this, but the best will be to
call Revenue Canada, as they'll summaries the laws your activities operate under. *don't hate me*
3) I read an insurance thread that made it sound like I won't be able to get insurance for more than 18 months and have to give all my destinations. Is it not possible to buy the insurance as I go? I had difficulties finding insurance for a 12-month trip. Didn't know you could have until 18 months, but beyond that period of time, you're just not interesting enough for them. Too risky I guess. However, maybe you could see if you'd get longer if you registered your business.
4) Do I have to be in Canada in order to secure visas for other countries? I will have a plan to a point but I'd like to be open to change along the way. Mike answered already, but I wanted to add that some visas take forever to have, some demands a letter of invitation prior to sending the visa request, some countries have no embassy/consulate in all countries. I guess you need to plan a little bit ahead if you don't want to be stuck somewhere.
5) Can someone please tell me what it means to be non-resident? It means you are losing the priviledges given to the residents of Canada. I think the most important one is the universal health insurance. And you only get it back once your return home and file the form again. Every province has difference on that issue, so you'd better call your government. If you are from BC or Quebec, there's a discussion about it
here.
Courageous project, I hope you'll keep us updated !