One thing my company has done since way back in its startup days (we're pretty successful at this point) is put an emphasis on working reasonable hours, and it's been successful for us. Some people still choose to work long hours because they're excited about what they're working on, but it's not expected or asked of anyone. There were two reasons for doing that even as a startup, and I think they're both still valid.
Reason #1 is that working long hours often becomes an excuse to not prioritize properly. Working under realistic constraints forces you to really decide whether some feature is worth it, or if spending 40 hours on Feature A is better than spending 40 hours in Features B, C, and D combined. Too often the answer at companies is, "Well, A, B, C, and D are all really important, so just work harder and do everything." That's a very seductive trap to fall into, but it's absolutely the wrong escape valve. At least in my view a failure to focus and prioritize properly is far more often a cause of failure for startups than "we didn't work hard enough."
Reason #2 is that you want to avoid burning people out if you expect to be around for the long haul. Our company just turned 10, and we still have a surprising number of long-tenured engineers, which I'd attribute in large part to the work environment and the relative sanity of the work/life balance people can have. If you expect people to work 60+ hours a week every week, they're not going to stick around for 10 years; they're going to get burned out and bored and they'll feel like the only way to get a break is to quit.
You can quibble with the second reason, but I think that even in a situation where you feel like you have to get a ton done and working 40 hours a week isn't an option, it's very important not to use "we'll just work harder" as an excuse to avoid making the hard decisions around priorities.
Reason #1 is that working long hours often becomes an excuse to not prioritize properly. Working under realistic constraints forces you to really decide whether some feature is worth it, or if spending 40 hours on Feature A is better than spending 40 hours in Features B, C, and D combined. Too often the answer at companies is, "Well, A, B, C, and D are all really important, so just work harder and do everything." That's a very seductive trap to fall into, but it's absolutely the wrong escape valve. At least in my view a failure to focus and prioritize properly is far more often a cause of failure for startups than "we didn't work hard enough."
Reason #2 is that you want to avoid burning people out if you expect to be around for the long haul. Our company just turned 10, and we still have a surprising number of long-tenured engineers, which I'd attribute in large part to the work environment and the relative sanity of the work/life balance people can have. If you expect people to work 60+ hours a week every week, they're not going to stick around for 10 years; they're going to get burned out and bored and they'll feel like the only way to get a break is to quit.
You can quibble with the second reason, but I think that even in a situation where you feel like you have to get a ton done and working 40 hours a week isn't an option, it's very important not to use "we'll just work harder" as an excuse to avoid making the hard decisions around priorities.