In the opening the pawn-majority is not felt as a major factor, but its significance grows rapidly through the middlegame, and often becomes decisive in the endgame. Dražen Marović, Dynamic Pawn Play In Chess
A lead in development is at its most useful in open positions or in situations where the active side can achieve a central breakthrough. Luděk Pachman, Complete Chess Strategy 3: Play On The Wings
If a backward pawn sits on a half-open file, it might be weak. If it isn't on a half-open file, the pawn probably won't become a significant weakness. Jeremy Silman, The Reassess Your Chess Workbook
The real purpose behind "knights before bishops" is "keep the widest choice" or, as it is generally expressed, "reserve the greater option." Cecil Purdy, Action Chess: Purdy's 24 Hours Opening Repertoire
The best time to study an opening is immediately before and/or immediately after a game, because then the stimulus to learn is at a peak. Leonard Barden & Tim Harding, The Batsford Guide To Chess Openings