@Simon3074 You should never let an Inquiry or Request expire. 23 hours should be enough time for a guest to respond to questions, although if your guests are from a much different time zone, it's a bit more challenging, so make sure to respond to their request with your questions asap.
You kind of have to impress on guests the need for a timely response. They don't know the host has to make a decision to accept or decline within 24 hours.
So ask your questions, and say something like "I will need a response to these questions by 3 pm EST in order to process your request." If they still don't answer, and the 24 hours is almost up, you will have to decline.
Guests who fail to respond within a few hours, unless it's the middle of the night where they are, are generally a red flag, but some guests fail to turn on their notifications, so may not be aware that they have a message waiting.
Before a booking is confirmed, you don't have access to their phone number, so you can't phone or text them. So all you can do is decline if the answers to your questions are crucial to your acceptance.
Letting an inquiry or request expire is counted against your response rate, which is used in the assessments for Superhost, if you care about that. Declining affects your Acceptance rate, which isn't so crucial, and doesn't factor into Superhost, although Airbnb likes to send threatening messages if you decline "too" much, whatever that is.
But hosts have reported having pretty low Acceptance rates, and Airbnb hasn't suspended their listings or anything.