Hello, there. I can only reach 1 and 5, also. It can be hard to play fast octaves. Sometimes I slip because I can barely reach. But, I wonder if I have an advantage with octaves, because it is my max stretch . . . less estimation to get used to . . . just keep my hand open and there it is. But then again, I get fatigued more quickly because I'm at my max.
The ability you will miss out on, coldness, is playing legato octaves. I prefer to play sixths with alternating fingers for legato, and I wish I could do the same with octaves. If you can reach with the fourth finger, I would suggest practicing that way, so you can make use of it when the music calls for it. From what I understand, that is reason many pianists use 1 and 4.