Okay, to get to the southern tip of spain from me is going to be the best part of a week in any landy, so we'll call it a week. Now, I THINK (I dont know, newbie idiot!) That most of what I want to see/experience is in sputhern africa (botswana, zimbabwe, zambia, SA, lesotho, angola? Etc,) so if I spent a month there, maybe two, and then 1.5 weeks to travel through northern africa each way, so lets say 8-12 weeks? I doubt it will be my last trip (certainly hope not!)
Another option Ive heard of, but not looked into, is the santander ferry, which goes to spain in about as long as it would take to drive, iirc.
Okay, lets just rule out some things, I cant drive through the middle east, correct? And even if I could, it would be unwise to go to certain bits of eastern europe, currently. So that means the only way to drive is via the ferry from spain to morocco