In my current job, I haven't worked a weekend in the 6 months I've been there, even though I am on-call to support a 24/7 environment. Also for the first time ever, I'm working somewhere with a formal flexi-time system. I'm expected to work my 40 hour weeks on average, and if I go into debt by more than 8 hours or get more than 24 hours into credit, I can expect my manager to query why - They don't want me doing excessive overtime, as it tells them that either I'm taking on too much or I'm not using my time effectively.
In previous jobs, where I had no formal on-call requirement, I was frequently asked to work weekends or long hours. This was usually due to unrealistic expectations and lack of resources. Once, I was even told by a manager "If you're not putting in 40% overtime, you're not pulling your weight". That was the day I started a work to rule, and while that manager was working there I never worked more or less that 40 hours each week.
Normally though, I'm happy to work long hours to meet a deadline, as long as it is recognised that for every hours of overtime I do, it is going to cost at least an hour of under-time in the future.
Under-time can take many forms. The best form is flexi-time, work a 60 hour week to meet a deadline, get a couple of days off the following week off to recover. Another is informal, work a month of 60 hour weeks, spend the next month drained and working at half effectiveness. The worst is having someone put under so much pressure that they have a breakdown and get signed off on sick-pay for a couple of months.
I've seen all of these and experienced several.
Sure, working the odd weekend can show willing, but if it happens too often you need to discuss with your manager why and what can be done to compensate you for your time. A good manager will know that for knowledge work, just paying you overtime is not going to do anyone any good in the long term.
It's a trite phrase, but it's about work-life balance. There's a reason that 8 hours sleep, 8 hours work, 8 hours play has become the norm. Deviate too far from it at your peril.