We're in a similar situation. I think you've got it basically right, but probably with some modifications that I think you'll find work significantly in your favor. Here's how I see it working in American terms, maybe some Canadians can translate :-)
You are correct that you need non-pension funds to bridge the gap between the date you stop working and when your pensions and Social Security (CPP/OAS?) kick in. I think you're overestimating the amount though. Assuming a 4% rate of return (corrected for 3% inflation, meaning a 7% real rate of return), you would need about $350,000 saved up in order to last you 15 years, spending $2,500/month. Now, that figure assumes you draw down the principal as well, such that you would have exactly $0 on the day your pension kicked in, so you can modify as you see fit. And of course that example assumes everything works perfectly according to plan, which won't happen. But anyway, you don't need anywhere near $600,000 or $750,000, probably only half that amount.
If you want to end up with some assets when you start taking your pension (not eating up all the principal over the 15 years), then you need to either have a bigger stash saved up, defer quitting longer, earn side income thru part-time work, live on less, or some combination of all of these.
Another possibility is one of you bites the bullet and works, say, for one extra year (quitting 14 years before pension starts instead of 15 years), where you can effectively save about 100% of their income to really add to your stash.
Another possibility is starting one or both of your pensions earlier, if your work allows that. You would likely get a lesser amount, but it would also help you bridge that 15 year gap at perhaps only a small penalty.
It's a bit of a tricky problem, because you have to balance wanting to leave, having enough saved, not shorting yourself out on your pension, but also not "hitting the jackpot" too late in life when all the deferred pensions/etc. kick in, but when you also might not enjoy the financial freedom as much. So I hear ya. But in all, it's a very good problem to have.