Been doing my Namibia research and here's what I'm thinking as far as post-Cape Town goes. Conceptualizing Cape Town to Victoria Falls as being broken into two segments:
1. 2WD. One Way. Capetown up the west side for Ais Ais, Fish River Canyon, Sossusvlei, Swakopmund, Skeleton Coast, Etosha, drop off car in Windhoek.
Place -> Place: (est segment drive time) (est cumulative drive time) (est days to transit)
Cape Town -> Ais-Ais, Namibia: 800km (2-3 days)
Ais Ais -> Aus: 333km (1133km) (2 days)
Aus -> Sossusvlei: 378km (1511km) (2 days)
Sossusvlei -> Swakopmund: 403km (1914km) (2 days)
Swakopmund -> Palmwag: 435km (2349km) (2 days)
Palmwag -> Okakuejo: 307km (2656km) (1 day)
Okakuejo -> Tsumeb: 247km (2903km) (3 days)
Tsumeb -> Windhoek: 432km (3335km) (1 day)
16 days driving, not counting additional days stopped. Not sure if those estimates are conservative enough, or if I should be padding them with more days? Outside of the major highways, I'm using 60km/hour and ballparking 200km/day (80km/hour & 400km/day for major highways).
Based on those estimates, 30 days seems like overkill and perhaps 21-22 days is a more reasonable estimate. Definitely want at least 21 days as that is where the car hire average daily rates drop significantly.
2a. 4WD. Loop. Windhoek thru Caprivi Strip, down into Chobe/Okavango/Maun, return vehicle in Windhoek. Fly to Vic Falls.
Windhoek -> Divundu 914km (3 days)
Divundu -> Kongola 201km (1115km) (2 days)
Kongola -> Ngoma 174km (1289km) (1 day)
Ngoma -> Mababe 205km (1494km) (1 day)
Mababe -> Maun 118km (1612km) (1 day)
Maun -> Windhoek 810km (2422km) (2-3 days)
(10-11 days not counting stop days)
2b. 4WD. One Way. Windhoek thru Caprivi Strip, down into Chobe/Okavango/Maun, loop back up thru Chobe, return vehicle at Kasane. Bus to Vic Falls.
Windhoek -> Maun 810km (2-3 days)
Maun -> Divundu 425km (1235km) (2 days)
Divundu -> Kongola 202km (1437km) (2 days)
Kongola -> Kasane 121km (1558km) (1 day)
Kasane -> Mababe 367km (1925km) (2 days)
Mababe -> Kasane 367km (2182km) (2 days)
(11-12 days not counting stop days)
Guessing those estimates are probably a little too aggressive and need to have a couple of days of padding added in. Even with adding 2-3 more days to bump the ranges up to 12-15, that still seems like it can comfortably accommodate an 18-21 day car hire after adding in another 6 days for stops.
Was leaning toward the 2a option over 2b, but not strongly. Now leaning toward the one way, as those into/out of Windhoek segments look brutal.