Use early and late hours well, keep the middle of the day flexible and expect more people.
What changes in summer
The useful variables are daylight, temperature, crowd level and which surrounding areas are easy to access. Build the day around those rather than expecting Bled to feel the same year round.
Use the best hours
In summer, early and late hours are usually the most comfortable. In winter, daylight is shorter and a warm indoor stop in the middle can make the day much more enjoyable.
Day trips
Bohinj, Pokljuka and Kranjska Gora can feel completely different from Bled in the same season. Check conditions before committing to higher roads or mountain routes.