And if i stay lots of days in a row...?
If you are at 14 hearts with your spouse then a few nights won’t do much harm. Give loved gifts next two days and all will be well. If you’re at 11 or less your spouse will likely be in bed when you get back.
You can’t count on your spouse to run the farm. As for the animals they won’t die, but they might get grumpy if you don’t have auto-petter, auto-grabber, and full well stocked silos. Their produce quality might decrease slightly and they will not produce on days not fed (manually or automatically.) Nothing will happen to your crops, save maybe a lightning strike, but that can happen anyways. They just won’t grow the days not watered (sprinklers solve this), but they will all die if the season changes while you are gone (save those in your greenhouse.)
Do NOT enter volcano until WELL equipped with Space Boots, Lava Katana sword at very least, Galaxy sword best. Ruby ring or iridium bands. Also good quality food preferably with speed boosts and triple espresso. You will also need a good watering can upgrade if you haven’t already. You will have to take it in the volcano even though not needed for regular mines. You will likely pass out in mines a couple times until you get hang of the flames.
But there is plenty to do do on island without exploring volcano. Including a small farm that acts like a greenhouse once you get enough golden walnuts to use it. That’s where you will sleep over.