It can be difficult to be hard and fast with this rule, but you don't have to be hard and fast, just sort-of. There will always be jars that appeal to you that are not in your particular sub-category and of course you'll want to pick them up. But having that general goal can really help keep that collection corralled into something manageable.
No one has a goal at the beginning, but after you've been looking around for a while, there will be a certain company or perhaps a type of design that you're drawn to. Those are the jars that will be calling your name.
You know exactly what I mean. It might be Brush jars that you really love or perhaps you don't care about a particular company, but like "pig cookie jars". If you can specialize in one or two different areas, it helps with the decisions about buying later on.
I've also known folks who "specialize" by the number of jars, only sticking with e.g. 100 jars, always selling or getting rid of one when a new jar is added to the collection.
