I remember when I got my Fuga, saying to one of the shop guys it was the last bike I was ever going to buy (to which he laughed). 2 more bikes later, within 4 years. I bought my steel Merckx because it was a deal I couldn't pass up, and I wanted a beater (it's the world's nicest beater, btw ). Then I decided riding outside all winter was more fun than riding the trainer, so I sold my trainer and bought a winter bike. I use it more than I thought I would, like whenever it's going to be wet out, and whenever I need to carry stuff. It's a great addition to the stable. I do a lot more utilitarian cycling.

But you don't need to/shouldn't go into debt for more bikes. Wait until you have a need for, and the money for, a new bike. You might be surprised what you end up wanting.