plastic tanks have a 10 year life span. After that you are pushing you luck, especially if the tank gets direct sun.
the repeated heating and cooling of the tank, combined with clumsy delivery drivers leaning on the tank messes with the weld around the horizontal centre line of the tank.
steel tanks rust and drip, which is why people went plastic, but the plastic nearly always fails on a winter delivery. The tank has been weakened enough over the summer, that the 2T weight of a 2000L delivery of winter fuel splits the seam,and the top 1000L ends up around the drivers ankles.
We have gone a bit quiet at the moment, but now the weather has turned nippy, we are expecting the work to pick up quite dramatically again (it does every year)