I just started racing this past season and went down this same road. Some say yes and some say no. Many say just get a 2nd pair of racing wheels. Some say you should train on the bike you race with so you are familiar and comfortable on it. I thought about it for a while then found a great deal on a frame and over time bought all the components to build up my race bike. You can save tons on ebay and online stores but you have to know what you are buying.
I mostly ride my race bike but will ride my "other" bike once or twice a week. 4000 miles is not that much for a decent bike. This topic has been covered a lot here so do a search and see what others have to say if you don;t get a lot of replies to this thread.