The more repeat/regular clients you have, the less effect does out of office mode have, and you’ll get some over time. If you get an order or two soon after you’re back, and can finish and deliver quickly, that should help.
Also, as most people say, it takes a few days up to a week to pick up again anyway, and if you are able to and want to “bite the bullet” of having to reply to messages, you could consider turning off out of office mode a day or two or three before you’ll be back, so it won’t take so long to pick up once you’re actually back. In that case, of course, align with your delivery times.
Don’t be too afraid of that mode, though, some days of not having to reply to messages are invaluable … Ah, talking about that though, people who bought from you before, can message you even while in out of office mode, only new people can’t (unless you allow it per checkbox choice), so while in theory you don’t need to reply within 24 hours if you talked to them before, you might want to reply anyhow if they are return and good customers, so the option of longer delivery times (to avoid people ordering and you having to deliver while out of office) but replying to messages might yet be a good choice, especially if you might get messages from former customers and want to reply to those, they might be fine with a longer delivery time if they know you’re briefly away but if they’d not get any reply for days, might look for another seller.
Anyway, some really free time is important too, try to find a balance that works for you.