I have a visa for Namibia until the 18th of December. I would like to take a bus from Windhoek to Capetown that leaves Windhoek on December 18th in the afternoon. It would get me to the NAM/SA-border at around 2 a.m. on December 19th.

What will likely happen at the border? Is this seriously not a good idea? Is it possible to extend the visa for only a couple of days?