Literally hundreds of times.
Here’s a relic: It’s a TEC Route “calculator” that was issued by the FAA Western Region (this was before FSDO’s) in 1977. You’d look for your departure airport on the left and then you’d slide the white card down until the little arrow pointed to your destination airport, and then you’d see the appropriate TEC route name, route, and altitude in the window at the bottom of the card.
You can see that these were the “Charlie” routes. Now we’re up to “Papa!”
BTW, you do not need to pre-file an IFR flight plan if you are going to fly between airports served by a SoCal TEC route. You can just call up Clearance Delivery or Ground and tell them you want the SBA Papa 6 to Santa Ana, for example. No problemo.