Remember that boosts are only re-calculated when you trigger actions to the market. So, even if someone else supplies or withdraws an asset from the market and your market portion is changed, your boost is not re-calculated until you additionally supply or withdraw from the market. A user gets the boost at the time of the last action. Even though the qScore decreases with time, your boosts will not be decreased unless you trigger actions to the market. Thus, user is eligible to have a strategy to do no actions so that gain his boost as maximum as possible until they lock more QBT tokens. However, once the user has zero qScore (i.e., lock expires), the user can be kicked out. Anyone can kick the user by sending transaction to the "QubitLocker" smart contract and applying zero boost to the user who has no qScore at that point.