"Are couples allowed to sleep over 'here and there'?" No. But 99 percent of the time no one would know or care. But since you've already told people you plan to, that's a little more awkward.

Most people I know who live with their unmarried partner are "out" to their ex-pat friends, but tell everyone else they are married. So they are married at work, married to compound security, married at the gym, married when trying to get into the family section at the tennis last weekend. They don't wear rings and no one asks for proof, so it's really easy to pass as married.