I also have the same situation as you mentioned, then i called back the manufacture here. I told them i used the pump 5-6 times per day and used it nearly 4 months. (My baby is 4.5 months old)
Then they said i used too much! Medela Swing is targeted for use 2-3 times per day only. They suggested if i use it so often like 5-6 times per day, it's better to buy "Free style"!
Since my pump got 1 year guarantee, they replace a Brand New one for me.