You've already undervalued yourself(your time) by giving 7 days for a part time job- for a year. They want you to continue working that ridiculous commitment(without suitable pay) by promoting you. I was in your position sortof. I went from one unrelated job to my career job- while working another job. I undervalued my time because I was happy with the total pay from both jobs. Unbeknownst to me, in retrospect I was smart because I was concentrating on my job for the first few years. It took offers from competitors to make me realize what I was worth. But even then if I worked 6 days, I demanded perks. I wouldn't give more than 5 days(part or full time) without some incentives beyond a redefinition of the job to full time(unless you were getting valuable benefits with the change.)