Insulation will not be perfect so if you have the heating on when not needed, as is likely to be the case for 24/7, some will be wasted. In any case the low level you refer to would still have to be high enough to be comfortable for you so can't be too low.
As for whether continuous or pulsed heating is cheaper, I suspect there's no difference long term as I'd expect it to be the same number of watts (except for the loss through your insulation mentioned above).
I don't know if the saving is significant though. Eddie has made a good point. It's more to do with timing when it is on at all, if you want savings. If you are under the bedcovers, why have it on ?