Why does God keep heavy burdens lingering on earth for years rather than take them on to Heaven ?

There is a reason for everything that happens. For one thing, I'm speaking from my own experiences in life .... when we have to endure in this life, it's makes us stronger! It has me. I'm undergoing chemo/radiation right now for breast cancer. This is my second time around for cancer. I still give God the praise and glory for my situation because I know in the end it's going to make me a better person. I can understand you asking this question. Sometimes it's hard to understand from our human viewpoint, how and why we must endure burdens. God does tell us to ... "Cast every burden upon him"....doesn't matter how big or small it is. He will see us through and give us Victory!!