Sure, it is possible for a bomber to go over several SBR mission.
But from a statistical point of view it is not a good move.
Bomber do on average: 3.5 damage.
Bomber ma ybe shot down: 1/6 * 15 = 2,5 damage to the attacker.
If I have not done mistake the average gain of SBR is 1 IPC.
However in the real game, it may happens that bomber is shot down on first attempt. A loss of 15 IPc.
Or it is never hit and continue to destroy enemy IPC. A great drain of IPC from the enemy.
IMHO, SBR is one of the area of A&A where statistic is less useful. There are too few dices involved and the result is totally umpredictable.
Sometime gambling is awarded with a big prize!