You would have in your collection a wide range of art in your collection where there would be some old art and surely new ones. Surely, the begging question would be whether your old art would be valuable as it has been around for many years now. Unlike antiques, the older the art is does not mean that it would worth more money compared to the newer ones but surely it is worth something.
As a matter of fact, earlier works from the artist would usually worth more. And this does not matter whether the artist is popular or not. Art differs from other collectibles because if the artist is not popular, then the technique would be. This is where you can bank on the way the art was produced if the artist is no longer famous. If you know where and who to show these art to, coupled with the relevant information about the way it was produced, you will be able to pin-point to the time when a specific technique was popular.
If you are unsure, you can head towards the museums where the permanent collection of art are located. This is where you will be able to associate your collection with a specific time frame. You will find that early art work are more serious. They are more passionate because they are produced at a time when the artists are setting out to establish their names. Making quick comparisons, you will find that an earlier work and later ones differ in terms of richness where you can garner more detail and perhaps more emotions because it is seldom that an artist can continue to adopt a similar technique and effort from day one.
Apart from that, early artwork are way more exploratory and hence becomes more expressive. This is where you can get the raw experience exuded by the artist when they were younger and more inexperienced. Artworks then were made without having a permanent artistic direction as they are more open to new opportunities. Do not be too surprised if you keep a piece of work from an artist which uses a totally different media as compared to what he or she is known today. For example you might have a sketch using charcoal of an artist who is today known for digital art. Now, you might find that to be a bit different but it shows 2 very important elements. The first is the influence and the process and the second is what the artist thought art was in the past. Perhaps, charcoal sketching was a popular medium at that time which will then illustrate your intention of buying that piece of art at that time.
After all, you must be very aware that artists are constantly changing their artistic styles and techniques and they would not have derived their current persona without having to try everything that they possibly could. An artist would need to try something until there is a demand and market for their work because they would not know what is required out there. Once they have found a certain footing which suits them most, where they can produce easily and demanded in the market, they will then develop that style and method to establish themselves in that area. So, would their early works be valuable? Surely.