Things to do before Big Bang

High leveled 3-lined shields will be better than 20 attack shields depending on it's level. If it's a maple shield either the low level or the high level one would get curb stomped by either a 71+ or 121+ shield.

Which brings me back to my first question, whether it'll be worth it to sell off the 20 attack shield for cash to cube items in the future, - if the price will fall by that time.
Especially when a 3-lined shield can beat it.