A board that is strong now will not stay strong forever.
As other players level, hit higher-cost 2-stars, and improve their boards, the same board gradually starts losing.
Think of the period where your current strength is enough as the shelf life of your board.
You do not need to win every round. Win while your board is strong, accept weaker periods, then win again at your next power spike.
Suppose you are playing a 2-cost reroll comp.
Hitting your 2-cost 2-stars early can give you a very strong board for that stage of the game.
But as more players hit 3-cost 2-stars, that same board starts to fall off.
The pattern might look like:
Hit 2-cost 2-stars → strong
Lobby starts hitting 3-cost 2-stars → your board falls off
Hit your 2-cost 3-star → spike again
Your 2-star board has a window where it is supposed to win.
If your 2-cost 2-star board is strong now, use that window to preserve HP.
Once the lobby catches up, you may need your next spike—such as a 3-star—to start winning again.
That next spike costs gold.
Every extra round you survive gives base income, plus interest when you have it. If you preserved HP earlier, you can afford to lose some rounds after your board falls off while your economy grows.
That lets you roll later with more gold and more chances to hit.
If you already lost too much HP during the period when your board was supposed to be strong, you lose that option. You may be forced to roll earlier with less gold simply to avoid dying.