There are a few factors that would determine the number of days required for one to cover all the hill stations in Kerala. And that include the number of stations you want to visit; the amount of time that you want to spend at each location; your travel time and the kind of activity you would like to indulge in at these locations.
Among the many hill stations in Kerala, some of the most popular ones include Munnar, Wayanad, Idukki, Vagamon and Ponmudi. Wayanad is noted for its wildlife sanctuaries, trekking trails and waterfalls. Idukki is home to Asia's first arch dam and offers stunning views of the Western Ghats. Ponmudi is known for its breathtaking views of the surrounding hills and valleys. Taking into account the location and distances between these hill stations, and if you are not interested in a tightly-packed, hurried tour then you would at least require eight days in Kerala.
The information given below may be considered as a suggestion for your hill station itinerary:
Days 1-3: Munnar
Days 4-5: Wayanad
Day 6-7: Idukki
Day 8: Vagamon or Ponmudi