I agree 100% with the prior posters. This is the kind of advice my mom gave me when I had my baby, and it came from a good place - she wanted me to get a break! - but, it's no coincidence that she only breastfed me for four months, when she supposedly "dried up." It's a story we see every day here. So we're not just hard-core "fundamentalist" breastfeeding advocates - we've seen what a slippery slope supplementation can be. Sure, one bottle every couple weeks probably won't hurt, but one bottle a day can reduce your supply, and then you supplement more ... and you get the picture.
I agree with PPs. Either have your husband help you in other ways, or pump and give him breastmilk in a bottle to give your LO. In a couple months, when your supply is better established, you may have more flexibility if you want to do part-time breastfeeding. Breastfeeding doesn't have to be an all or nothing thing, but the first few months are a sensitive time, when your supply is still getting established.
I do think it's a generational thing. Remember, most women in our mother's generation did not breastfeed, and almost NONE of our grandmothers did. The art was almost lost - a whole generation skipped it, and the basic rules were forgotten. So sometimes we need to be careful about the advice we're hearing. Even an experienced grandma who is wonderful with babies may not know much about breastfeeding.
I didn't get four hours of sleep ever, for about 14 months, but I was fine. I was tired, but I don't think it did me any permanent harm. But most babies sleep better than mine. Anyway, four hours sounds like a GREAT stretch of sleep to me!