As a self-drive destination, how you spend your time depends on what you're after. Here's a rough guide.
Two weeks or more
Two weeks is ideal for covering the route in both directions: from Cape Town along Route 62 to Oudtshoorn, then the coast through Plettenberg Bay to an Eastern Cape safari, before returning via Tsitsikamma, Knysna, and the Whale Route.
One week or more
One week can work well if you prefer to linger in the coastal towns of Knysna and Plettenberg Bay with a wildlife finale. We'd suggest flying out from Port Elizabeth to save time.
Three to four nights
We generally recommend a minimum of three full nights on the route itself. A guided tour is usually the better option here. It takes the stress out of driving and lets you see more in less time.
Less than two nights
This isn't quite enough time to do the route justice. We'd suggest a shorter stay in Hermanus or the Winelands instead, since the Garden Route rewards a slower pace.