The only reason you'll stop is when you milk the game for all it's worth, mastering the gameplay to the point that you end up getting infinite scores more often than you don't
If its controller uses the first effect, they won't have enough LP to use the second
If it's a "contract", you'll be able to use "Demis" as well
When it comes to Romin, A typical non-duel due to lines that say they are not interested in dueling or lack of dueling knowledge in the work
If youre self milling a lot then maybe you want Timeless Witness, and there are effects like Unnatural Restoration that lend themselves to counter-based strategies
If youre new and feel intimidated by not knowing the most powerful cards, just go with your gut and pick the cards or abilities that appeal to you - even if thats just choosing your favourite Disney characters