Oven Takes A Long Time To Heat Up

My oven takes a long time to heat up to temperature. The pre-heat indicator will turn off well before it actually gets up to temperature, but the oven will get to temperature in roughly a half an hour, based on my findings from using an oven thermometer. I tested out both elements and the temp sensor over the weekend with a multimeter, and they tested out good. Does anyone have any clues for me on what else I could check?