You asked

How long can someone go without a lot of sleep?

Most adults need between seven and nine hours of sleep per night. If you start forcing yourself to sleep less than your ideal number of hours, eventually the sleep deficit will catch up to you. Being sleepy during the day can affect you in many ways; you may feel fatigued, drowsy, experience mood swings and become depressed. If you are continuously sleep-deprived, you will have trouble learning new things, doing complex tasks or doing repetitive tasks.
The indirect effects of sleepiness are more dangerous than the direct ones. Continuous lack of sleep can cause you to fall asleep while driving or when operating heavy machinery. Less dramatic, but equally serious, is the chance of repeatedly falling asleep while on the job, even if it is office work, as it can have a detrimental effect on your career.
Trying to “catch up” with sleep on the weekends is not a good long-term solution. Cut down on your waking hours or try not to have successive nights with too little sleep. If your new baby is keeping you up at night, arrange a shift system with your partner to minimise your sleep loss.

More questions

Being sleep deprived does not make for a happy relationship. If you’re suffering from lack of sleep, there are a few things you can try.
It is very important that you do not use sleep remedies, including the herbal variety, before talking to your doctor - they could have an adverse affect if you are breastfeeding.
When the argument you are having involves your children, it is a much better idea to have this fight behind closed doors, away from your children.
Making sure your newborn stays healthy and happy is as much about common sense as it is about care and washing hands is one of the simplest ways to ensure it.
If you find that you and your mother are locking horns over child care issues then it’s time to assert your wishes.
Most people agree that fighting in front of children is inappropriate. However, many people also agree that, as long as your child is brought up in a loving, warm, free home, they will learn that the occasional disagreement between their loving parents is simply a part of life.
If your child is big enough you might consider a star chart for good behaviour. Each time your child goes to bed without any trouble, he or she gets a star. If at the end of the week he has seven stars on his chart then he gets a special treat.
Choosing to change child care after your parents have been looking after your child for months or years can be a delicate subject but, handled correctly, it can be done.
The right amount of sleep differs from individual to individual and even between cultures.
Negotiating the changes in friendships that a child brings can be tricky for any new mom, but it is possible.