If there is a year left before expiration, the person selling the warrant will want to sell it for more than $10, since there is a chance the stock price could move up within that time, making the warrant worth more. Therefore, the warrant could actually be sold for potentially $12, instead of $10, as an example.
What does the warrant expiry date mean?
Expiration Date: This is the date the warrant expires. ... The more time remaining until expiry, the more time for the underlying security to appreciate, which, in turn, will increase the price of the warrant (unless it depreciates). Therefore, the expiry date is the date on which the right to exercise ceases to exist.