Firstly, let me start by saying that this is not a case of one size fits all, and there are sometimes specific factors that can push a business in either direction.

So should you advertise on Google on weekends? In most situations, I think the more important question is…

Are your customers searching for your products/services on weekends?

And if you’re not advertising on weekends, will prospective customers simply go to your competitors instead?

But I’m not open on weekends and don’t want to be handling phone calls on weekends

That’s perfectly reasonable. Every business owner needs a break to refresh and recharge. But have you considered that other busy working people are also taking a break from work? And this might be their one chance to research and find a product/service provider (like you)!

4 important things to consider when thinking about weekends:

1. Just because we’re advertising on Google on weekends, it doesn’t mean that you have to be working and be handling inbound calls and emails on weekends. In fact, most customers won’t expect you to. Why not sign off email on Friday afternoon, and then sign in first thing Monday morning, and follow up any enquiries which have come through over the weekend? And as far as phone calls go, most people won’t expect you to be handing inbound calls on weekends. It’s just vital that you have a professional sounding and compelling voicemail message in place to strongly encourage people to leave their details so you can follow up on Monday. Or better still, have you considered a live answering service? That way you’ll never miss anyone, can capitalise on the people searching on weekends, while also having a chance to enjoy yours! And you can simply follow up first thing on Monday morning. 
2. We’ll always optimise based on performance on weekends. If weekends happen to be more likely to attract ‘window shoppers’, and don’t convert quite as efficiently as weekdays, that shouldn’t be a concern. We’ll feed this conversion stream data back into our machine learning and optimisation systems, and will always optimise based around this, for example in bidding less aggressively on weekends to bring conversion efficiency and ROI inline with weekends.
3. There are a significant number of people who will ‘Google’ you on the weekend to do their research, and then call you on a Monday/Tuesday to take action. So don’t be alarmed if you don’t get a massive number of enquiries on the weekend itself. Because oftentimes being ‘findable’ on the weekend means you’ll just have a stronger Monday/Tuesday in terms of enquiries.
4. Weekends are almost always quieter in terms of search activity. For most businesses, a Saturday/Sunday typically has half the search activity as a typical weekday. So yes, weekends are quieter, but in many situations, that certainly doesn’t mean they’re not worthwhile.

What’s the bottom line?

For most businesses, it DOES make sense to keep Google Ads active on weekends and that’s what most of our clients do. Generally, it doesn’t matter what day or time people are searching — if they’re searching for your products and services, why would you want that business to go to a competitor?

We generally encourage businesses to have us advertise 7 days a week, and see how it goes over a period of a few months. And of course we’ll always optimise based on performance to ensure we’re delivering the very best possible ROI.