2006 lbz,one local dealer recomends drop pan and replace the filter and fluid, next dealer says flushand change fluid leaving the filter in. First dealer says this is what allison recomends every 25,000 miles. I thought this was for severe service only, I don't tow. I just drive keeping my foot out of it most of the time. I have 30,000 miles with every thing stock, I have changed external filter twice and would like some input for longlife. Thanks.