Like others, I try to stick to a theme. But, as Jessie mentioned, "something shiny attracts my attention", and off-subject I go. The biggest detriment to that plan was during the years I worked for a hobby shop and got kits at "cost" or as extra "compensation" for the low wages. I think my collection blossomed to over well over 2500 kits during that time, although I had a good start already. At 60, I still like 1/72 aircraft. I'll build most any scale of aircraft, but that was the scale I started in so many years ago. Before someone mentions the usual about 1/72 - in the larger scales, the sub-assemblies can be as daunting as a 1/72 kit, yet the model gets finished. So I don't go for the,"the parts are too small" concept. But, I digress... My current collecting "Theme" is WWI aircraft. I usually stick to a theme for several months or until I burn-out on the subject. I try to tell myself that this helps motivate me to complete kits, but the number of built kits usually doesn't count as a measure of that concept. As my wife says, I'm a hopeless polystyrene addict. Build on! Ric