Quicksilver's ability is limit once per phase. The villain phase is separate from the player phase, so you can (and should) exhaust Quicksilver to defend on every Villain attack you can, since he will instantly ready after doing so, and this will NOT prevent you from readying on your next turn.

If going all in on the Protection aspect, you can even exhaust to defend an attack that targets you, ready Quicksilver due to his Super Speed ability, and then Exhaust to defend an attack targeting another hero. You won't instantly ready after the second attack, but if you have Always Be Running that may not be a huge issue.

Quicksilver combos very well with a teammate running Leadership, so you can stack up Attack and Thwart buffs like Lead from the Front and Morale Boost on a turn you have several copies of Always Be Running and smash the villain or main scheme with multiple huge hits.

Aggression also works great, since Friction Resistance combos very nicely with Jarnbjorn.

One trick I have found that really brings Quicksilver up to another level is knowing when to flip to alter ego. If you already have Friction Resistance (the best card in the game) and Serval Industries out then just flip down to alter ego on the turn when there are between 9-5 cards left in your deck. Check your discard pile. If there 2 Maximum Velocity left then shuffle 1 Maximum Velocity and 1 Always Be Running back into your deck on the turn you go down otherwise shuffle 2 Always Be Running.

On your next turn in alter ego form 1st shuffle 2 more Always Be Running into your deck. Then look at your hand. Depending on how many of the good cards you drew you and how many cards are left in the deck you can either use Superpowered Siblings to discard 2 cards to hopefully draw the last 2 always be runnings or just wait until the next turn if the majority of the cards are still in the hero deck. (The goal is too have as many of them together in a single turn as possible.)

Best case scenario is this. You go down with 5 cards left in the deck with 1 Running or Maximum still in there. You go down to alter ego and shuffle 2 more into the deck leaving 7 cards in it. Next turn you draw 6 cards leaving 1 card in the deck. You shuffle 2 more into the deck making it now 3 cards in the hero deck. You use Superpowered Siblings to discard 2 cards and draw 2 to hopefully draw the cards you just shuffled into the deck.

Unless you are very unlucky you now have 1 Maximum Velocity and 4 Always Be Running in your hand plus an extra card you will use as a resource with Friction Resistance to play Maximum Velocity.

You will be doing 1(Base ATK)+2(Max V)+1(Reinforced Sinew) X 6(4 always be runnings and his normal 2 activations)=30 damage. If you have Combat Training, #3 Adrenaline Rush, you can increase that to 48. This can be done fairly reliably each time you are close to decking.

Personally I think this now makes Quicksilver the most powerful hero in the game for multiplayer. (I even think there is now an argument to nerfing him a little bit as this is a ridiculous amount of damage in a single turn.) You can obviously also remove tons of threat instead with Heroic Intuition and Civic Duty.