When I worked at my first startup, I got put on support engineer duty. My job was to be the engineer first-responder for any customer support tickets that came in that day. Customer Support would triage the tickets and if they thought it was a bug, it would come to me. I would fix it, and then send it back.
I got really, really good at fixing bugs, reading/parsing other people's code, and then mimicking their style so that it looked like their code all along. Pretty fun.
It was a startup, there were about 10 engineers. I would show up around 8:30am and work until 7:30am, getting lunch and sometimes dinner with my coworkers. I worked very hard and tried to get to inbox zero day. Sometimes a ticket would come in at 5:35, and I'd sigh and tackle it and try and get a fix out before I left. (Note: by "push" I just mean put a PR up, not actually deploy it, because obviously it needed review and testing.)
One night, miracle of miracles, I had a date. And I was supposed to meet her at 7pm, which meant I needed to leave the office at six so that I could get home, change, then meet her. I had four (4) tickets left in the queue. Normally I would have tried to push fixes for all of them before I left, but I didn't. I just left, and I went on my date. No 2nd date, if you're curious.
The next day I showed up at work at 8am, a little early, because I knew I didn't finish everything the day before.
Nobody said anything.
Nobody complained.
The customers responded with "thank you for fixing this so quickly!" even though I had waited overnight.
I had an epiphany -- which is probably obvious to many of you reading this right now. I realized that I had been busting my ass for no good reason. I realized that there is ALWAYS more work. I realized that nobody really expects any non-emergency work to get done after 5pm, even in start up culture. (If they do, they're lunatics that don't respect you as a fully realized human being and you should find another boss.)
I started showing up at 9am and leaving at 5pm. Sometimes I made it through my tickets, sometimes I had a handful leftover. I fixed them all in a timely fashion in 1-2 business days instead of <1 business day, and my boss gave me high marks. I got promotions, I got raises, I'm now very successful, imo.
That was 11 years ago, and ever since I've kept a pretty strict work/life balance. I try really hard to leave work at work and enjoy life after. My company doesn't own my life -- they pay me for 9-5. If they want more time, they pay more money. In fact, I consider overtime to be even _more_ expensive than my regular salary.
All of that said... do I do things on the weekend? Sometimes. Maybe. Mostly personal projects. But I do it because I want to, not because anyone else expects the work to be done. And there is a special carveout for on-call rotations and after-hours emergencies where I may need to respond to something, but I tend to work out comp time instead. For example, if I have to spend 4 hours on a weekend to fix something, I get to check out a few hours early on Friday.
So I guess... it depends. But don't work extra hours unless you want to. Nobody reasonably expects it, and as a salaried employee, you don't get paid extra for it. Nobody's going to remember that you worked til 10pm every night, but they will remember that you never came to their birthday parties. Just keep that in mind.