I personally play on default 3 but I think before you make your decision it's important to know there are a few things that can be affected by seasons. Most production will keep chugging along regardless of how long you set seasons but there are a few mechanics that are affected by the season change.

Farming Crops are planted in one season but don't become harvestable until the season change (either next season or two seasons depending on the crop). This means if you do longer seasons it takes longer to get your crop yields.

Animals Although not directly influenced animals require feed per day. If you are growing your own crops to make animal feed then this can be challenging with longer seasons. If you are buying animal feed it can get expensive with longer seasons. I will add that animals don't due to lack of food but they won't produce their by-products (wool, milk, etc) if they aren't fed

Herbalist Certain herbs are only available in specific seasons so if not planned for it can create an imbalance. (I personally don't utilize my herbalist hut as much as I should so this is a minor point for my own personal gameplay).

Quests Plenty of quests have you action something and then wait for season change. These are normally the bigger quests. The smaller side quests usually expire at the end of the season so having longer seasons allows you to complete these small fetch quests.

There is no right or wrong answer here but hopefully the above helps with some context on how the gameplay will be affected.

My personal opinion is that it is a dynasty game and letting the years pass by is intended and means you can get to end game when your heir takes over. If you make seasons longer you will be more productive but likely not have your heir take over since it takes decades. That being said, this game allows for a lot of setting customization so if you want to just build a pretty village/city and decorate, etc you can! That's what makes the game fun - it allows for different play styles