I think living together is not a taboo anymore. When my hubby and I started off, we spent weekends on his house consistently without my mom knowing. After 2 years, we decided to go to Singapore and my mom made no fuss about it. When we came back, I just casually said na sa bahay kame mag-stay. After a year we got married.
For us, we never formally talked na 'o let's move in together' it just fell into place. My mom was open about it probably because I was on the right age and I already proved something to her particularly being responsible.