Short answer
Begin with Taipei and nearby day trips. Around a week, add Taichung or Sun Moon Lake. At 10 days or more, southern cities such as Tainan and Kaohsiung become easier to justify. For repeat trips, stop adding cities and choose a region or theme instead.
In this guide
The first-trip expansion logic
Taiwan is compact enough to tempt travellers into adding too many stops. Take the opposite approach: start in Taipei and expand only when the trip length earns it.
Taipei first
Use Taipei as the first base. Jiufen and Shifen appear as day trips, not new overnight bases.
This keeps a short trip simple and gives you city, food and easy excursion variety without forcing a hotel move.
Around a week: add one central option
At around a week / 7 days, adding Taichung or Sun Moon Lake can work.
Treat that as a choice, not an instruction to add both. Avoid rushing through too many stops.
10 days or more: southern Taiwan becomes realistic
At 10 days or more, consider Tainan and Kaohsiung for food, temples and warmer southern conditions.
Again, this is route-expansion guidance rather than a fixed allocation of nights or days.
Let season change the region
Spring and autumn are the easiest broad periods for city walks, day trips, cycling and outdoor sightseeing.
Summer strengthens islands and beaches but brings more heat, rain and typhoon exposure. Winter shifts value towards hot springs and the warmer south.
Mountain and East Coast plans need more weather flexibility than city-based travel.
Repeat trip: choose a theme
For a return visit, consider planning around one stronger theme: hot springs, tea mountains, night markets, cycling, coastal road trips, food, heritage towns or offshore islands.
That is often more coherent than repeating a first-trip checklist with extra stops.
Final decision
Shorter trip: Taipei first. Around a week: add Taichung or Sun Moon Lake. 10+ days: southern Taiwan becomes a realistic extension. For repeat travel, choose a region or theme and give it more depth.