Spending 5 days in Krakow is not too much, especially if you do side trips to Auschwitz, the salt mines and Zakopane. However, I would consider 7 days to be too long as Krakow is not a huge city and its city center is very compact. In this case, you could add 2 or 3 days in Wroclaw and Warsaw.

Seven days in Krakow is not too long and is actually considered the "sweet spot" for a relaxed, comprehensive visit to Poland’s cultural capital. While you can see the Old Town and Wawel Castle in two days, a week allows you to explore the city's deeper layers and take essential day trips. Two days are typically dedicated to the heavy historical sites: one for Auschwitz-Birkenau and another for the Wieliczka Salt Mine. This leaves you with three to four days to explore the vibrant Jewish Quarter (Kazimierz), visit Schindler’s Factory, and enjoy the city's legendary "milk bars" and jazz clubs without feeling rushed. With seven days, you can also take a day trip to the Tatra Mountains and the town of Zakopane for hiking or thermal baths, or visit the Częstochowa monastery. A week-long stay lets you experience Krakow's famous atmosphere—slow coffee in the Main Square and long walks along the Vistula River—rather than just checking boxes.

Spending 7 days in Krakow can be a wonderful experience, as the city offers a rich blend of history, culture, and vibrant atmosphere. Whether it’s “too long” depends on your travel style and interests. Here’s a breakdown to help you decide:

Why 7 Days Could Be Perfect:

1. Explore Krakow Thoroughly:
   - Wander the Old Town (Rynek Główny, St. Mary’s Basilica, Wawel Castle).
   - Visit Kazimierz (the Jewish Quarter) and learn about its history.
   - Take time to enjoy the city’s cafes, museums, and local cuisine.

2. Day Trips:
   - Auschwitz-Birkenau Memorial and Museum (a must-visit, but emotionally heavy).
   - Wieliczka Salt Mine (a UNESCO World Heritage site).
   - Zakopane and the Tatra Mountains (for nature lovers).
   - Other nearby towns like Tarnów or Częstochowa.

3. Relaxed Pace:
   - With 7 days, you can explore at a leisurely pace without feeling rushed.
   - Spend time soaking in the city’s atmosphere and enjoying its nightlife.

Potential Downsides:

1. If You’re Short on Time:
   If you have limited vacation days and want to see multiple destinations, 7 days might feel too long.

2. If You Prefer Fast-Paced Travel:
   Krakow is compact, and its main attractions can be covered in 3-4 days if you’re moving quickly.

3. Limited Interest in History:
   If you’re not particularly interested in history or culture, you might find fewer activities to fill a full week.

Recommendation:

If you enjoy immersive travel and want to explore Krakow in depth, 7 days is a great amount of time. You can balance sightseeing, day trips, and relaxation. However, if you prefer a faster pace or want to visit other Polish cities (e.g., Warsaw, Gdańsk, Wrocław), consider splitting your time.

Ultimately, Krakow has enough to offer to keep you engaged for a week if you plan your itinerary thoughtfully!