I would set a date a week or two in advance and tell your mom you're thinking of going home then. That will give you both more time together and maybe an opportunity to do some more talking. Do you have room for your mom to come down and visit you at all? Maybe you can plan another trip for 6 months from now or establish an email or snail mail, phone or online contact habit?

I think if you set a date to go home, it will be easier for you to enjoy the remaining time with your mom.