We rebuild the page closest to your sale and run it against the one you have now, on your own live traffic. The scoreboard is revenue per visitor, not a dashboard metric.
Usually the product page, because that is where the money is decided. One page, rebuilt properly, rather than a list of opinions about twelve of them.
Old page and new page live at the same time, your visitors split between them. Seasonality and ad spend hit both equally, so the result decides.
Two or three tests a month after the rebuild, each one run to a clear answer and kept or dropped on what the revenue says.
Fewer opinions, more tested changes: if the rebuild does not lift revenue per visitor, you keep your money.