For an adult or older child, you can upgrade to an intermediate viola after a couple years of dedicated practice. If you are comfortable getting around on the instrument and you’re mastering the fundamentals but can't get the sounds and emotions from the instrument that you want, it might be time to look into stepping up. If it's a smaller or younger child, even though you can trade in an instrument as he or she steps up, it might be prudent to wait until they won't be experiencing any more growth spurts before you get that top-of-the-line viola.