I'm one of the more cautious parents, but I did just that in April. DD2 is 17, 18 in August, and DD3 was just days from her 16th birthday. We left them at home with their two dogs while we travelled to visit DFil, who is very unwell, for 6 days. DD1 (19) is not safe to be left, so she went to my parents' house.
We left them a schedule of tasks (bins, dishwasher, washing, cats, rabbits) and a meal plan with all meals scheduled and ingredients bought. My parents live 1 mile away and visited each morning to check in on them. We had WhatsApp messaging and video calls.
However, they both have SN which means that they are unlikely to leave the house, don't have lots of friends, wouldn't have a party, etc.
They did really well. We had a spatula casualty (DD3 took 'smash burgers' literally), but we were able to have one delivered the next day to replace it. Otherwise, no issues.
We're going out again in August, but this time we're putting the dogs in residential training and taking DD2 & DD3 with us because 9 days seems too long.