Fallout 3 uses several timeskips at the beginning of the game showing how the main character grew inside of the shelter. Is this bad practice? In what situation should you use this? Also, when doing this should you make the scenes particularly long. I was thinking that using 4-5 panels would be too short, and you need to make a timeskip scene last 20 panels or so, especially when they're jumbled one after another like that at the beginning.
Love the Opening First:
The pacing of written stories works differently than in graphic art. If you are just trying to write a comic or video, this can work. You would need very deliberate written information for a comic in the scenes to explain what is happening. But for a comic, this is quite appropriate. You will need to be sure the reader is clear about what is happening. A video game is similar, and with the added advantage that you can involve the gamer in the story (although the challenges are greater, because the player has to WANT to be the main character and live in your world).
But it wouldn't work in a written format. There is a lot of commitment to painting an opening scene in a book that provides the reader context to the main character and story. In a medium like movies or comic books, you can flash through a lot of material very quickly that creates impressions without a lot of information. But in writing, you need to provide information that creates those impressions.
That is the heart of show-don't-tell. A comic is quite literally showing you. In writing, You provide information to create impressions, not just providing the the information. Giving information is infodump. You risk alienating your reader with too much shifting up-front. You want the opening to draw the reader into the story.
There are ways you could do this in writing. For example, if you are writing in first person, you can have the character open the story by literally introducing themselves. In that case, you are using a semi-acceptable snuck-in infodump to fill with the details of the character. In that case, you are trying to use them talking to create an impression of the kind of person they are. If you were planning to write third person, you could switch to third person after a short first-person prelude.
A similar approach for a comic can be used, with the main character narrating the opening frames as if talking about themselves.
But for the most part, these details should unfold gradually as the story advances. I think of the opening of Bioshock where you are describing the game mechanics and world history through an opening level, but then you really get to understand the character in parts throughout the game. You discover the backstory of the character organically over time. You describe the character's thoughts about their past. They have dreams about that really formative event that influences the upcoming scene. A trauma causes them to relive a similar trauma. The past comes up in conversation, where they bitterly compare someone else's petty parental problems with their own horrific abuse.