No. I can only talk about vented machines, but in a well designed, vented machine, the lint that does make it past the filter will disappear out of the vent. There will be a little build up in the vent, but that's not a big problem. In the case of our machine, the way the rigid tube carrying the air from the filter to the rear exhaust was mounted meant that it kept coming loose and air (and lint) that should have been contained and passed out of the vent would leak a little into the space under the machine.
As the air inlet was under the machine, this meant that when it built up, clumps of lint could be sucked into the machine and straight onto the heater elements. We first noticed this when we smelled burning. We also found a number of char patches within the heater.
Ours could manage to be pretty full after a couple of months and that was with cleaning the filter every time.
We ran ours for its last 12 months on half-heat, but only because it had two identical elements and used both for full heat, but one had failed - probably due to overheating when covered in a ball of lint - and I couldn't be bothered with the time and cost of replacing it when we were planning to get a new machine anyway! Running half heat on it still had the remaining element at the same temperature, so just as much risk of it igniting - possibly more, as the inactive element right next to it could accumulate a bigger build-up.