We have 2 DDs, aged 10 and 12. They are both sensible, reliable, trustworthy and get on well together, so we (and they) are happy for them to be home alone together.
DH and I both work FT, but have taken off one week in August together and we will have a 'holiday' then (just visiting family in various parts of the UK). We have also each booked off either a Thursday or a Friday every week so that one of us is with the children on those days.
My DM will have them for the day on Mondays as she only works the end of the week, she'll be around Tues and Weds mornings too, so they can hang out with her if they'd like to (she lives about a 20 minute walk from our house), but I suspect they'll just make these mornings their 'chill out time' and will relax watching YouTube and Netflix in their PJs on the sofas! I finish at 2 on Tues and 3 on Weds, so will be home shortly after that. DH works 10 minutes walk away, and I'm 7 minutes by car so we can both be home pretty quickly in an emergency.
Both girls have front door keys and phones with trackers on them and we will allow them to venture out to the park 5 minutes away from home or the shop (less than a minute away) whilst we are at work, as long as they stay together and text us to let us know before they go.
It's a huge mindset change from previous years where they were too young to be left alone for more than 15 mins or so, but I think having the eldest start Senior School and the fact that they both travel to and from school on their own and let themselves in when they get home (an hour before either DH or me), means that all 4 of us feel confident that they are ready - we practised a bit over the Easter break and they're going to spend most of Tuesday and Wednesday this week (half term) home alone, which they're looking forward to.
It's amazing to think that we've mostly made it through the 'paid childcare' years now - when I think of all the thousands and thousands of pounds it has cost us over the years, and how there was one August where I ended up nearly £50 worse off for having worked 3 days a week whilst having to pay for childcare for the 2 of them...