For me, it depends on the model. For aerobatic models like my Extra, power changing pitch trim messes with flying the sequences, so it's something to trim out.

But for flying a scale cub or even a trainer, I use the elevator trim like the full scale guys do. I change it to match the airspeed I want to fly at at the moment. If I'm roaring around with the trainer, doing the "trainers can't do that" thing, then I add in a bunch of down elevator trim. When I'm flying down the field backwards in a breeze or just floating around, I add in the up trim. If I'm shooting touch and goes and messing around with slips and one-wheel landings, then I'll trim somewhere in the middle to make the landing approach look like what I want it to look like at the moment.

Remember, elevator trim controls your airspeed, throttle controls altitude. Elevator trim isn't a "set it and forget it" thing for that type of model. So don't be afraid to adjust the elevator trim during the flight depending on the model and how you're flying it at the moment.