Hiking to Summit of San Jacinto Peak via Deer Springs in Idyllwild.

I'm doing this hike approximately 18.5 miles round trip want to do it as a day hike. I have heard it takes approximately 12-14 hours. I'm not sure what the fitness level of the person quoting that time was and if they stopped at all or often, etc. Has anyone here done this hike and have some details you can share bout it? Thanks so much! Audra