This is excerpt from Choice of Games Style Guide document which I think can be applied to for this question.
- Too much text between options can be boring.
- After about 100–200 words of text in the main body, consider adding something for the player to do, even if it’s just a *fake_choice asking how the player feels about what’s happening.
- Avoid 400 words or more between choices.
Personally I try not to go over 200-300 words per “page” (until next choice or page_break). But I’m not published author so my approach might be wrong.