I believe (and I know I'll be corrected real fast if I'm wrong) that If you leave the both of you on the same PNR, both of you won't clear until the Silver is processed which is one day prior. However if you split the records (PNR), the plat will be processed on the regular schedule and the silver on the regular schedule. If the Plat clears and the silver doesn't prior to two hours before departure then the Plat is better off using the Companion upgrade at the gate which is first come first serve. That takes priority over the silver u/g.