At what age or stage of life should you start to downsize? i want to hang on to sentimental objects due to memories..

Depends on you.: This depends on who you are and what you consider sentimental. Hoarding is a very fast growing problem all over the country, and many people attatch memories, etc. To things, like milk cartons, etc.. Having said that, there are always things people accumulate over life that mean a lot. If the item is in good condition, and is clean, it should be no problem, but don't get trapped in your home.