Originally Posted by NuGuy

This isn't exactly accurate. It is true that reserves are able to go to the ALV+15, but only if they grab you while you're below the reserve guarantee. The reserve guarantee is the ALV minus 2. Once you reach your reserve guarantee, you are "Full" have have no further obligation to the company. For example, if you have 65 hours for the month, and the reserve guarantee is 74 (76 ALV minus 2). You fly a 2 day trip worth 10:30, and that brings you to 75:30 for the month. You are now over your guarantee, so you are done for the month. OTOH, if you flew a one day trip for 5:15, you'd now be 70:15, you could still be assigned a trip all the way up to the ALV+15 depending on the days of availability you have left.

Many pilots attempt to fill up at the beginning of the month so they fill up before they run out of days of availability. This is something reserves can preference for trip coverage.