Sometimes it's not so much the space as it is the temperature that keeps you in bed at night. You might run hot, while your partner wants to bundle up in layers of blankets and inch closer to you for warmth. A king size mattress can allow you to put some space between you and the living furnace next to you, while still permitting you to hold hands or at least sleep on the same surface. The wider king mattresses also allow a little more wiggle room for cover tossing; if you get hot, you can throw your side of the covers off without exposing your partner to frigid drafts.
You don't like to admit it, but those furry friends are great foot warmers on brisk evenings. Of course, the trade-off is that they take up some space. Well, a lot of space. Inevitably, your cuddly cats and dogs will sprawl out in the middle of the bed, leaving you with mere inches of sleeping surface. If you need some more space, then a king mattress may be the ticket. If your pets regularly stick to the foot of the bed, then the extra inches provided by a California king will do. If you find yourself separated from your partner in the middle of the night by a giant ball of fur, then you will want the extra width provided by the king mattress size.
Pregnancy and growing families
It's not the size of your partner's belly that makes sleep difficult; it's the army of pillows, coupled with all of the tossing and turning that pregnancy brings with it. If you want to stay close to your partner during those rambunctious nights, then a king mattress may help. Not only does the extra space give her room for any comfortable position imaginable, but it gives you room to sleep without constant disturbance. Plus, it will come in handy a few years down the road when monsters in the closet and spooky storms bring extra visitors to your room late at night.
Many partners switch to twin beds when old age or achy joints start to get the best of them, but a king mattress will give you the exact same amount of space as two twin beds while keeping the two of you close together. It's nice to reach over in the night and know someone is there, without having to navigate a giant gap between your bed and his.
Sears has a great selection of mattresses in many materials and firmness levels. If you are looking to upgrade to something bigger and better, stop in to try a few mattresses out and take home one that is right for you.