Al, Relieving some of the weight upon the tires
will help prevent what is called weather checking/cracking. Flat spotting is something not to worry about, but tires left in the same position, through various seasons will start to split on the sidewalls. The load on sidewalls can also lead to rust between the rim and tire sidewall. VERY much so if you have tires that don't hold air to proper spec's through the winter. It also pinches and folds the sidewall cords if the tire goes completely flat and the weight of the boat and trailer rest on it until you find out next spring. It can reduce the load bearing life of the tire. If this problem becomes severe enough it can lead to sidewall failure.A fairly quick and easy way to remove this load from the tires is to use a floor jack to raise each side of the axle(s) and slip a concrete block under the axle. This way the trailer rails stay properly tensioned by the weight of the boat on the bunks and the tires have no load. Blocking the trailer frame itself, if done improperly, can stress the frame rail beams.Because one side of my trailer's tires are 1/2 in snow and ice, and the other 1/2 in the sun, and because the otherside is in "Moordores" solid icy winter grip until late April I always block the axles up.Just some busy work to make me feel better while awaiting spring thaw.RayS/V Speedy