I've been doing this for several years. Before I started adding conditioner, I had a couple episodes of fuel gelling and wax crystals forming in and clogging the filter. This usually occurred when the temperature remained at about 0 F or below.
Since I started adding conditioner, no problems. I used to run all over looking for "Heating oil conditioner". Then I just bought diesel anti-gel. When that got hard to find, I just started adding a bottle (3 qt) of Diesel Kleen (white bottle) when my tank is filled. It contains an anti-gel and seems to work just as good.
My heating oil provider will deliver oil with the treatment included for $.04 per gallon extra, which works out to about $8 per tank. This is about half the cost of the Diesel Kleen, but I prefer to add it myself-that way I KNOW it's in the tank.
Also, I used to only add the treatment in the coldest part of winter, but it seemed that about once a year the filter element would become clogged (with dirt, not wax), so I started adding the diesel kleen on every fill, and I haven't had that problem since, either.
The other thing I did was move the filter inside the basement. When we did this we also changed the supply line from the bottom of the tank to exit the top of the tank, suspended about 1 inch from the bottom. The theory is that by suspending the line, any sludge laying in the tank that might clog the line before the fuel gets to the filter will not get picked up. Also, moving the filter inside is supposed to reduce the likelihood of wax crystals forming on the filter element.
I did all this at about the same time, so I can't say if just adding the conditioner, or just moving the filter inside, would have done the job. I also don't know if we've had winters as cold as the ones when the line clogged. I just know that it's working for me so far.
Of course, I'm sure it gets a lot colder in Nova Scotia than it does here in central PA, but the anti-gel is supposed to work to something like -30 F, if I recall correctly. The only trick is that you're supposed to add it before the heating oil gets below 32 F, I think. I think that's called the "cloud point". Once the temp of the oil reaches that point, the treatment is not effective.
I don't what the temp of the oil in the delivery truck is, or how they keep it above 32 F, especially if they load the night before and let the truck sit out all night. That makes me think that maybe all heating oil is "treated" anyway, but it's not something I can control, so I just dump the Diesel Kleen in the tank the morning I'm expecting the delivery.
Hopefully somebody smarter than me about these things will reply with better information about this subject.