Don't know if this helps or not with a Rotax engine, but the technique is useful in old car engines: If possible, crank the engine over a few times to build oil pressure BEFORE turning on the ignition! This gets lube to the bearings and cam surfaces before any real load is put on them.
I used a sump mounted Reiff type heater on my Cherokee for years - it worked really well, especially with a blanket over the cowl and the cooling ducts plugged. In the winter I would leave it on 24/7 with no adverse effects.
Another thing to remember is that it is a bad idea to put the engine through heating/cooling cycles when it is not running. This draws moisture laden air into the engine which "may" condense. If you do not keep the heater on 24/7, then only heat it prior to starting the engine - and run the engine at operating temps for a good half hour to drive out any condensation!