Who to ask for referee in this case?

If i start working full time after poly then during my first job i contacted my poly lecturers to be my referee. Then when i want to switch job, i can’t ask the people in my current job to be my referee right? If not they will know that i am applying for new jobs. But i am working at my current job for 3 years plus and if suddenly contact poly lecturer again later they forget who am i. What happen if i work for 10 years at first job then switch job? Then definitely can’t text poly lecturers for referee anymore though