My indoor plants have survived up to five weeks of our absence and a lot of abuse from neglect even when we're home but I'm not sure about three and a half months without a drink of water during a time when the house is even drier because of the furnace running. So I'm on a quest to find the best way to preserve them without having to ask someone in to water them.
I came across all sorts of suggestions online. Some of them quite pricey. The one that would probably work best for the time we're gone is an electronic watering system that waters up to 20 houseplants. Unfortunately it costs anywhere from $75-95 depending upon who you order from. For that amount of money I could replace all my plants.
There are fancy globes that you fill and invert but those only last 3-5 days. Homemade ones can last a little longer if you use a larger plastic bottle and invert it into wet soil but they're not guaranteed to work well either and certainly not for 108 days.
A makeshift greenhouse from a clear plastic bag sounds more reasonable as it would keep moisture in. That would work well for the smaller plants. My large ficus tree would need a plastic bag put around the container rather than the whole tree but still, it's a tough character and survives a lot of neglect although it complains by dropping leaves.
Another suggestion that might be workable is to fold a bath towel length-wise, lay it in the bathtub and place bricks along it. Plants would be set on the bricks and the tub filled with enough water to cover the bricks. Plants would absorb moisture through the holes in the bottom of the pots. For our lengthy absence, I would let the faucet drip to keep water in the tub. Trouble is, my pots don't have drain holes. So I may combine this idea with the next. A water wick.
I've tried this before and it worked but only for a short time since I did it with a bottle of water and a small wick. You place a saturated wick into moist soil at one end and stick the other into a container of water. The water wicks up and into the soil.
Here are two links to some of these suggestions for watering indoor plants while on vacation: