When you get to buy something that you are passionate about then life is exciting. If your passion is sewing you could spend days looking at sewing machine reviews to find just the right sewing machine for yourself. Getting a good machine can help you in the long run if you can get a reliable machine that can challenge you yet meet your demands or needs during that time period.
Some people grow out of their machine because they want or need something that their current machine does not provide. For example if they get really fast at sewing and they would like to complete their projects at a speed that they want to go instead of whatever the limits are of the machine then they want to upgrade.
It is not uncommon and if you play your cards right you can sell your sewing machine to help pay the costs for the new one.