I'm going on another river cruise next year. This time on Portugal's Douro River. I will probably spend a couple of nights in Lisbon before the cruise. I'd like to fly to Seville and spend two nights there first. I'd likely rent a car and drive to Lisbon, or maybe get a private driver. Question is: How long would it take me to drive from Seville to Lisbon?? Anyone done this?? Thanks.

The direct route is all by motorway (autopista), about 400 km and 4 hours. A more scenic route through Aracena and historic Serpa takes about an hour longer.
Remember if you drop off a Spanish rental car in Portugal, you will be charged a big relocation fee (in some cases you aren't allowed). Don't know about private driver, but is likely to be expensive.