Its very hard to give you an answer to your origional question "is this part of my learning curve".
I could understand if they were too small a job for you, and you only wont to take on larger jobs. I guess that would mean your round has developed and you aren't quite as desperate for work anymore. But wouldn't say it is a learning curve more a stage in your developement.
However, if you had the time and they where of an average size compared to your other customers and priced them well, you shouldn't turn down the work.
I can see what you are saying in your second post though, it all takes time to develope your round. So good luck mate.
Gerard