Seems normal to me. Now, if you start one and get half way done, then see another passion and start it too, then find another passion and start it also. That would be considered an anomolly (at least to me). I would think 4 planes on the work bench is the start of a problem. Oops! I just described me. Phaeton 90, scratch ME109E, Brian Taylor 75" corsair, and a swapmeet plane being setup. Now how you handle swapmeets determines how big a problem you have. Do you go with $1000 in your pocket and leave having spent all of it?
Edwin