I can get almost 20,000 miles on SQ for RTW which works out to $0.26/mile (for $5,000 fare).

If you do YVR for example, 4100 miles for $500 is $0.12/mile so just head out to Vancouver monthly.

Travel within Canada avoids any immigration issues and is pretty easy to get back to YYZ from YVR if flights are cancelled (not like being stuck in SIN for a day or 2).

These DO NOT include class of service bonuses.

www.milecalc.com is a great site to figure out what routes give the most value.