Sleep advice for new dads

My son is 3 weeks old and we're running on fumes here. We're trying the shift system where my wife sleeps 9pm to 1am and I take 1am to 5am. Even getting 4 hour stretches feels amazing now. Wife says sleep deprivation is temporary but love is forever, which is sweet but I also just really want 6 hours straight. Anyone else do shifts like this or have other suggestions?