They're not even close to valid. Rose and Walker were signed as young prospects, not first team players. They had far more preparation than any player we've signed for the first team because they we intended to load them out from the start.
What long-term approach? What are you even talking about?
Ok, your opening post poses the question: 'Do you think it's better to wrap up dealings early and/or before the season starts? If so, how much of a difference do you think it makes?' Whereas I think what you're actually arguing is that players who are signed earlier in the transfer window make more of an instant impact.
Yours is a tempting conclusion to come to but overall, when faced with the evidence, it doesn't stand up. As has been shown, many of our best players were signed late in the window and went on to have good first seasons with us. The benefits of a preseason with us are offset against the inflated transfer fees earlier in the window. At a guess, I'd say some of our best signings would not have happened if we were determined to do all our business early - we would have moved on to cheaper, more affordable targets and easier, more straightforward deals to close.