Obviously, you can't take a 3 lb 2 oz bat to the middle simply because it felt great in the shop when you swung it around 5 times. A long inning would wear your arms/hands down if the bat is too heavy for you.
Having said that, the swell position will change the swing weight which will affect the timing. Knowledge of what works for your game is critical and also will take the guess work out.
I have one match bats with rolled up counter weight grip, duck bill toe, thick edges and high spine. It weight 2-11.0 and picks up a lot lighter. It is good enough for long innings, sixes, you name it. It is a perfect match bat. Without the knowledge of its swing weight, willow density, and other factors, there is no way I can replicate this bat. Ever.