Why is my 1 year old suddenly unable to sleep through the night without mommy or daddy?

My daughter has always been a pretty good self-soother. Generally, she doesn't need to be rocked to sleep, and she can fall asleep on her own. Over the last week or two, she's waking up in the middle of the night and keeps crying until mommy or daddy go to her. She'll stop crying if we hold her and rock, but as soon as we lay her down, she starts crying again (this is after I've already covered the basics: clean diaper, pacifier, even a bottle). The last few days, we've both been up for 1-2 hours a night, so out of exhaustion, I bring her back to bed w/my husband. He doesn't mind at all (I think he likes it actually), but I'm concerned about the habit we're creating. I love the extra cuddles, but I fear it will be a hard habit to break if we continue this patter. Anyone been through this before? Any tips or advice?